Within three months, Mr. Mnuchin’s new firm had circulated detailed investment plans and received $500 million commitments from the Emiratis, Kuwaitis and Qataris, according to previously unreported documents prepared by the main Saudi sovereign wealth fund, which itself soon committed $1 billion. Mr. Kushner’s new firm reached an agreement for a $2 billion investment from the Saudis six months after he left government.

A New York Times report last month revealing the Saudi investments in the Kushner and Mnuchin funds raised alarms from ethics experts and Democratic lawmakers about the appearance of potential payoffs for official acts during the Trump administration.

But an examination of the two men’s travels toward the end of the Trump presidency raises other questions about whether they sought to exploit official relationships with foreign leaders for private business interests.

In the weeks after the election, Mr. Kushner made three trips to the Middle East, the last for a Jan. 5 summit in Saudi Arabia with leaders of the Gulf monarchies. Mr. Mnuchin that day began a tour through the region that was planned to include private meetings with the heads of the sovereign wealth funds of Saudi Arabia, the Emirates, Qatar and Kuwait — all future investors. (He cut it short after the Capitol riot, dropping the Kuwait stop and, in Saudi Arabia, meeting only with the finance minister.)

Mr. Kushner and his aides have sometimes cast his private firm, Affinity Partners, as something like a continuation of the Abraham Fund. On a four-day trip to Israel in March to meet companies seeking investments, Mr. Kushner’s team portrayed the firm as a chance to invest in the peacemaking potential of the Abraham Accords, people who heard the pitch said, speaking on the condition of anonymity.

Both Mr. Kushner and Mr. Mnuchin hired several aides who were deeply involved in the accords: A top executive at Affinity, retired Maj. Gen. Miguel Correa, is a former military attaché in the Emirates who later worked in the White House. Top executives at Mr. Mnuchin’s fund, Liberty Strategic Capital, include a former ambassador to Israel and a former Treasury aide who helped arrange meetings with Gulf leaders.

The transition from government work for one Liberty Strategic executive was so fast that his jobs appeared to overlap. A roster of 11 top executives and advisers provided to the Saudis by April 2021 included the managing director Michael D’Ambrosio, even though he was still an assistant director at the Secret Service through the end of May. (A Secret Service spokesman said that Mr. D’Ambrosio had disclosed his new employment to the agency and spent his last weeks there on paid leave.)

An organizational chart for Liberty Strategic Capital, Mr. Mnuchin’s new investment fund, that the Saudis were reviewing by April.

A former Treasury aide known as a close confidant had resigned in 2019 and was waiting for Mr. Mnuchin in the private sector. That confidant, Eli Miller, had been working with Persian Gulf sovereign wealth funds at Blackstone, another investment firm, and immediately rejoined the secretary at his new firm’s founding.

The path from public service to private investing is well trod by members of both parties. The two Treasury secretaries under President Barack Obama later went to Wall Street.

But Mr. Kushner and Mr. Mnuchin stand out, ethics experts said, for the speed of their pivots and for the sums they raised from foreign rulers they had recently dealt with on behalf of the United States.

The Saudi investment with Mr. Kushner was made despite an advisory panel’s objections about his lack of relevant experience, the absence of other big investors, a high fee and the “public relations risk” of his ties to the former president, according to the minutes of a Saudi Public Investment Fund meeting last June that were obtained by The Times. Ethics experts suggested that the payment could be seen as a bid for influence if his father-in-law returned to office.

Senator Elizabeth Warren, a Massachusetts Democrat, has urged the Justice Department to “take a really hard look” at whether Mr. Kushner violated any criminal laws.

Kathleen Clark, a law professor at Washington University in St. Louis who studies government ethics, said each fund raised different issues. For Mr. Kushner, she said, “the reason this smells so bad is that there is all sorts of evidence he did not receive this on the merits.”

But for Mr. Mnuchin, who was a successful investor before entering government, the biggest question is whether he was burnishing relationships as Treasury secretary that he knew would be useful to him in the near future, Ms. Clark said.

“If he was, that is an abuse of his office,” she said. “I don’t know if it is criminal, but it is certainly corrupt.”

Through a spokesman, Mr. Kushner declined to comment.

In a statement, a spokesman for Mr. Mnuchin denied that he had sought investments while in office and said without providing specifics that some of the details in the Saudi documents were inaccurate. The former secretary was returning to a decades-long career as a professional investor, the spokesman added, and the firm has diverse backers, “including U.S. insurance companies, sovereign wealth funds, family offices and other institutional investors.”

The Adviser and the Secretary

Before vying for Persian Gulf investments, Mr. Kushner and Mr. Mnuchin sometimes competed for influence in the White House. During the transition to the Trump administration, Mr. Kushner sought to install his own candidates as Treasury secretary, until Mr. Mnuchin caught wind of it and launched a countercampaign, recalled several people familiar with the efforts.

The two men had come from very different business backgrounds. Mr. Kushner had previously run his family’s real estate empire and owned a weekly newspaper, both with mixed results; Mr. Mnuchin had followed his father into a career at Goldman Sachs and made a fortune investing in Hollywood films and a California bank. They kept a cordial distance in the administration. But both took strong and sometimes overlapping interests in the Persian Gulf.

President Donald J. Trump with Jared Kushner, his son-in-law, and Mr. Mnuchin at a diplomatic meeting involving Israel and the United Arab Emirates. Doug Mills/The New York Times

Mr. Mnuchin had few business dealings in the region before the Trump administration. Yet he spent far more time there as Treasury secretary — and met far more often with the heads of sovereign wealth funds — than his immediate predecessors: He made at least 18 visits over four years to the Persian Gulf monarchies, compared with a total of eight made by his three predecessors over the previous decade.

Former Treasury officials who worked with Mr. Mnuchin said that his time there reflected the priorities of the White House, including Iran sanctions, combating terrorist financing and the Abraham Accords. They noted that fund chiefs could be useful conduits to the rulers of the region.

“He was a business guy who really knew how to do personal diplomacy, and they liked him,” said Michael Greenwald, a former Treasury attaché in Kuwait and Qatar who served in the Obama and Trump administrations. “So that was an effective tool.”

Many of Mr. Mnuchin’s contacts appear to have been informal. One of his first meetings with Yasir al-Rumayyan, chief of the Saudi fund, was a September 2017 breakfast at the home of Stephen A. Schwarzman, Blackstone’s chief executive and Mr. Mnuchin’s neighbor. Mr. Miller, the secretary’s chief of staff at the time and now a senior managing director at Liberty Strategic, also attended.

Mr. Mnuchin met with Mr. al-Rumayyan at least nine more times during the Trump presidency, including in Bahrain, Switzerland and a Treasury conference room, according to department emails that the group Citizens for Responsibility and Ethics in Washington obtained through the Freedom of Information Act and shared with The Times.

In addition to multiple meetings with the Qatari emir and other officials, Mr. Mnuchin met at least 10 times with the head of the Qatar Investment Authority.

“I will just do one-on-one with Mansoor,” he emailed an aide in 2019, referring to Mansoor bin Ibrahim al-Mahmoud, the fund’s chief executive. “We have communicated direct.”

Mr. Mnuchin also met five times with the heads of the two main Emirati funds, once at a Washington dinner hosted by the co-founder of the Carlyle investment group.

And he met repeatedly with the rulers of the Emirates and Saudi Arabia. That included a private meeting with the Saudi crown prince in Riyadh in 2018 shortly after the kingdom’s agents killed Jamal Khashoggi, a dissident and columnist for The Washington Post. And the documents suggest Mr. Mnuchin built a rapport with Sheikh Mohammed bin Zayed, known by the initials M.B.Z., who recently became the Emirates’ president.

Sheikh Mohammed bin Zayed, president of the United Arab Emirates. Frank Augstein/Associated Press

“I am available anytime to see you and His royal highness M.B.Z.,” Mr. Mnuchin wrote to an unidentified recipient in February 2020, planning a visit. “If possible it would be great for us to have a bike ride and dinner as we had discussed.”

Suggesting a blurring of the lines between government and business, he wrote to a top Treasury aide in December 2020, apparently about a meeting with Saudi Arabia’s Public Investment Fund scheduled to take place after he stepped down.

“Do we have any more info on PIF late January?” he wrote to the aide, Zachary McEntee, who accompanied him on Gulf trips that involved the Abraham Fund and later joined Mr. Mnuchin’s firm. A spokesman said Mr. Mnuchin was asking about a conference sponsored by the Saudi fund that he attended as a private citizen.

Two weeks before he left office, Mr. Mnuchin flew to the region for official meetings with leaders across the Persian Gulf, with the stated purpose of discussing sanctions, terrorist financing and other national security matters. The visit included a private lunch on Jan. 8 at the National Museum of Qatar with the head of the country’s main investment fund.

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The Trump Investigations

• Numerous inquiries. Since Donald J. Trump left office, the former president has been facing civil and criminal investigations across the country into his business dealings and political activities. Here is a look at the notable inquiries:

• White House documents investigation. The Justice Department has begun a grand jury investigation into the handling of classified materials that ended up at Mr. Trump’s Florida home. The investigation is focused on the discovery by the National Archives that Mr. Trump had taken 15 boxes of documents from the White House to Mar-a-Lago when he left office.

• Manhattan criminal case. The Manhattan district attorney’s office has been investigating whether Mr. Trump or his family business, the Trump Organization, intentionally submitted false property values to potential lenders. But new signs have emerged that the inquiry may be losing steam.

• New York State civil inquiry. The New York attorney general’s office has been assisting with the Manhattan district attorney’s investigation while conducting its own civil inquiry into some of the same conduct. The civil inquiry is focused on whether Mr. Trump’s statements about the value of his assets were part of a pattern of fraud or were simply Trumpian showmanship.

• Georgia criminal inquiry. Mr. Trump himself is under scrutiny in Georgia, where the district attorney of Fulton County has been investigating whether he and others criminally interfered with the 2020 election results in the state. A special investigative grand jury has been seated in the case, and as many as 50 witnesses are expected to be subpoenaed.

• Jan. 6 inquiries. A House select committee and federal prosecutors are investigating the Jan. 6 assault on the Capitol and examining the possible culpability of a broad range of figures — including Mr. Trump and his allies — involved in efforts to overturn the results of the 2020 election.

• Westchester County criminal investigation. The district attorney’s office in Westchester County, N.Y., appears to be focused at least in part on whether the Trump Organization misled local officials about the value of a golf course, Trump National Golf Club Westchester, to reduce its taxes.

• Washington, D.C., lawsuit. The attorney general for the District of Columbia sued Mr. Trump’s inaugural committee, saying it vastly overpaid the Trump Organization for space at the Trump International Hotel during the January 2017 inaugural celebration. The committee and Mr. Trump’s family business later agreed to pay $750,000 to settle the lawsuit.

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As for Mr. Kushner, he had made his highest goal in the White House the brokering of a Middle East peace plan centered on funding from Saudi Arabia and its neighbors. The core of the plan was to solicit investments from the Gulf that might persuade Palestinians to relinquish some of their demands for a future state. As the culmination of those efforts, he and Mr. Mnuchin organized a “Peace to Prosperity” conference in Bahrain that no Palestinian officials attended.

To court Gulf rulers, Mr. Kushner helped persuade Mr. Trump to make the first foreign trip of his administration a 2017 visit to Saudi Arabia. Shortly after a meeting there with Mr. Kushner, the rulers of Saudi Arabia and the United Arab Emirates led a blockade of Qatar, accusing it of supporting extremism. Qatar hosts a major American military base, and the secretaries of defense and state pushed for an end to the blockade, but Mr. Trump initially backed it.

Mr. Kushner returned repeatedly to the Persian Gulf — making at least 10 trips during the Trump administration, often to visit multiple countries — and formed a close alliance with Saudi Crown Prince Mohammed bin Salman. After American intelligence agencies concluded that the Saudi leader had approved the brutal murder of Mr. Khashoggi, Mr. Kushner defended the prince in the White House.

Mr. Kushner at a meeting in September 2020 with Saudi Crown Prince Mohammed bin Salman. SPA handout/AFP, via Getty Images

In December 2020, Mr. Kushner visited Saudi Arabia and Qatar on a trip billed as an effort to end their three-year feud, returning to the kingdom on Jan. 5 for a Gulf summit where they formally reopened relations.

“Jared led the diplomatic effort to heal the Gulf rift,” Mr. Kushner’s firm declared in a recent investor presentation.

Allies of Mr. Mnuchin, though, said he also played a leading role, in part by working closely with Qatar to police terrorist financing and improve relations with Mr. Trump.

In reality, diplomats said, the resolution was driven by the Saudis’ desire to end the rift before the start of a new American administration. But credit for ending the blockade may be valuable in courting investments.

Exit Strategies

Mr. Mnuchin wasted no time getting back to business. Three weeks after the Trump administration ended, he said in an interview that he had a plan but wasn’t ready to discuss it.

By April 2021, his firm was showing potential investors a detailed list of target industries, according to documents obtained from the Saudi fund. The firm had arranged a legal structure that enabled foreign sovereign wealth funds to invest in strategically sensitive American industries, the documents show, and had already hired several former Treasury and State Department officials as top executives.

Mr. Kushner got off to a slower start. Even by the time he reached his $2 billion agreement with the Saudi fund last July, he had not hired any executives with relevant investing experience.

From left: Maj. Gen. Miguel Correa, Rabbi Aryeh Lightstone and Avi Berkowitz, whom Mr. Kushner hired for his fund. From Left: Bob Collet/Alamy Stock Photo; Steve Mack/Alamy Stock Photo; Mark Lennihan/Associated Press

He brought on his closest aide, Avi Berkowitz, and General Correa, the former military attaché. The general had left the U.S. embassy in the Emirates after clashing with senior diplomats who believed he had held unauthorized private meetings with the country’s leaders about arms sales and other matters. He had nonetheless been elevated to the White House, where he worked closely with Mr. Kushner. Career diplomats said that by the end of the administration, General Correa and Mr. Berkowitz were sometimes the only Americans accompanying Mr. Kushner to meet with Persian Gulf officials.

Mr. Kushner also hired Rabbi Aryeh Lightstone, a former diplomat in Jerusalem who had worked on the Abraham Accords and been named a director of the Abraham Fund.

A December 2021 presentation Mr. Kushner’s firm shared with potential investors, reported last month by The Intercept, suggests his firm’s focus may be blurring. As investment targets, the presentation listed a grab bag of high-growth industries including media, technology, health care, finance, consumer services and sustainable energy.

But the presentation also touted Mr. Kushner’s “geopolitical experience” and role in Middle Eastern diplomacy.

Mr. Kushner has continued to link his private firm to the Abraham Accords. “If we can get Israelis and Muslims in the region to do business together it will focus people on shared interests and shared values,” he recently told The Wall Street Journal, apparently referring to Muslims in neighboring countries (though about 20 percent of Israeli citizens are Muslim). The fund has so far invested in two Israeli companies.

Adam Boehler, a finance official and Mr. Kushner’s college roommate, oversaw the Abraham Fund. Ali Haider/EPA, via Shutterstock

The Abraham Fund was overseen by Adam Boehler, at the time the head of a newly formed development finance agency and a college roommate of Mr. Kushner’s. Mr. Boehler joined Mr. Mnuchin on his Gulf visit in October and accompanied Mr. Kushner to Qatar and Saudi Arabia in December.

Officials said the fund would invest in poorer countries that joined the accords, and its first projects were said to include upgrading checkpoints into Israel from the Palestinian territories and building a gas pipeline between the Red Sea and the Mediterranean.

Neither project went anywhere. Nor did the efforts to enlist Gulf money.

In January last year, Mr. Boehler announced the only publicly disclosed investment in the Abraham Fund: a “commitment of up to $50 million” from Uzbekistan, a relatively low-income country. Uzbek officials said at the time that they sought to reduce poverty and foster regional cooperation. Long criticized for human rights abuses, Uzbekistan had begun a lobbying push in Washington to improve its image after a leadership change; its new president also gave Mr. Trump a $2,950 silver replica of a historic building and his wife a $4,200 bed cover.

But no money for the short-lived Abraham Fund was ever delivered.

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Ben Hubbard, Isabel Kershner and Maggie Haberman contributed reporting. Kitty Bennett contributed research.

Kate Kelly covers money, influence, and policy as a correspondent in the Washington bureau of the Times. Before that, she spent twenty years covering Wall Street deals, key players and their intersection with politics. She is the author of three books, including "The Education of Brett Kavanaugh."

David D. Kirkpatrick is an investigative reporter based in New York and the author of “Into the Hands of the Soldiers: Freedom and Chaos in Egypt and the Middle East.“ In 2020 he shared a Pulitzer Prize for reporting on covert Russian interference in other governments and as the Cairo bureau chief from 2011 to 2015 he led coverage of the Arab Spring uprisings.

A version of this article appears in print on May 23, 2022, Section A, Page 1 of the New York edition with the headline: Quick Funding For Mnuchin And Kushner.