Born into poverty in rural China, Mr. Guo, whose current age has been variously characterized as 53 to 56, developed a refined style, preferring tailored Brioni suits and luxury cars. When Federal Bureau of Investigation agents raided his properties last year, they found two mattresses worth $36,000 each, a $31,000 bed, a $140,000 piano and several cars, including a Bugatti Chiron Super Sport, a Lamborghini and a Rolls-Royce.

In exile, Mr. Guo mounted a campaign in 2017 to discredit China’s anticorruption chief ahead of an important Communist Party meeting that fall. In doing so, he built up a large following of supporters both within China and among the vast Chinese diaspora, though his claims about corruption in the top ranks of the Communist Party couldn’t be substantiated by The New York Times.

That same year, the Chinese government mounted an unsuccessful campaign to repatriate Mr. Guo, tapping Steve Wynn, the finance chairman of the Republican National Committee who ran a casino resort in the Chinese territory of Macau, along with Elliott Broidy, the deputy chairman, to persuade Mr. Trump.

By then, Mr. Guo had become a member of Mar-a-Lago, Mr. Trump’s Palm Beach, Fla., club, and had begun bringing prominent allies of the president into his orbit, including Mr. Bannon later that year.

As the 2020 election approached, Mr. Guo’s U.S.-based media network, GTV, attempted to influence the election by promoting fabricated contents of a laptop belonging to Hunter Biden, a son of then-candidate Joe Biden. After the election, his network helped fund the so-called Million MAGA March in support of Mr. Trump. Mr. Guo also helped finance a court challenge to Mr. Biden’s election victory in Georgia, Mother Jones magazine reported.