But the full scope and intensity of Mr. Broidy’s activities, and the investigations into them, are only now coming into focus. Interviews and records show that:

• Federal investigators are homing in on the question of whether his involvement with the government of the United Arab Emirates and the Malaysian financier may have run afoul of FARA.

• Investigators are exploring the financial links between Mr. Broidy, the government of the United Arab Emirates and one of that government’s advisers, George Nader. According to previously unreported banking records, Mr. Nader was paid millions of dollars by the United Arab Emirates as he was working closely with Mr. Broidy on two fronts: to win security and intelligence contracts from the Emirate and Saudi governments, and to direct and fund the campaign in Washington against Qatar.

• Other banking records show that the government of the United Arab Emirates continued to pay Mr. Broidy’s company tens of millions of dollars, including a payment of $24 million in late March, even as it became public that prosecutors were looking into his activities.

• Officials from one country with which Mr. Broidy has worked, Angola, say they believed his company was being paid to lobby on their behalf, rather than to provide private intelligence services, as Mr. Broidy’s representatives say.

• His efforts to help his clients in Washington were more extensive than previously known. They involved not just prominent political figures but also payments to influential think tanks, lobbyists and a nonprofit conservative media outlet that produced articles promoting his clients’ agendas and criticizing their rivals.

Four people Mr. Broidy worked with on business or advocacy efforts have been indicted. He resigned as deputy finance chairman of the Republican National Committee last year after it was revealed he had agreed to pay $1.6 million in hush money to a former Playboy model he impregnated, in a deal arranged by Michael D. Cohen, the president’s former lawyer.

Business Was Good, and Then It Wasn’t

Mr. Broidy’s current situation is a sharp turnabout from two and a half years ago, when he helped raise a record $107 million for Mr. Trump’s inauguration. He offered to arrange inaugural tickets for politicians from Angola, the Republic of Congo and Romania — countries from which he sought intelligence contracts worth as much as $266 million, documents and interviews show.