The medical examiner’s office did not explain the timing of its announcement, nor why the findings took so long. Officials there had said as recently as Wednesday that it would not imminently release its findings, only to reverse course the next day. His death remains the subject of a police investigation, though spokesmen for the Metropolitan Police Department and the F.B.I. in Washington declined to comment.

For months, Mr. Lesin’s fate has been the subject of much speculation. In the Russian news media, he was said to have had a falling out with a major shareholder of Gazprom Media, Yuri V. Kovalchuk, an even closer business ally and friend of Mr. Putin’s. Some speculated that he had fled to the United States in a kind of self-exile, one that is not unknown among ministers and businessmen who once were in favor inside Mr. Putin’s Kremlin.

Karen Dawisha, a professor at Miami University and the author of “Putin’s Kleptocracy” about corruption among Putin’s allies, said that Mr. Lesin’s close ties to the Kremlin and its formal and informal controls over the media made him an improbable exile in the United States. “He knew more than most about the system’s dark center,” she said.

Mr. Lesin began his rise to power in the Russian media after the fall of the Soviet Union, leveraging a successful foray into advertising into a top government post and, eventually, a lucrative job as an executive at Gazprom’s media branch. He served as a minister overseeing the media from 1999 to 2004, a period that coincided with Mr. Putin’s first term as president and a steady expansion of state control over television in particular. Mr. Lesin was an instrumental figure in those efforts to take control of the country’s media. He later served as a presidential adviser, with a mandate to help develop the government’s growing technology and media apparatus.

Mr. Lesin’s wealth, and his holdings in the United States, had already attracted suspicion. In July 2014, Senator Roger Wicker, Republican of Mississippi, asked the Justice Department to investigate what he said was suspicion of wrongdoing under the Foreign Corrupt Practices Act. He cited Mr. Lesin’s properties in Europe, the British Virgin Islands, and Los Angeles, saying the Los Angeles properties were worth $28 million. He also suggested that his close ties to Russians subject to sanctions, including Mr. Kovalchuk and the bank he built, Bank Rossiya, warranted an investigation. “That a Russian public servant could have amassed the considerable funds required to acquire and maintain these assets in Europe and the United States raises serious questions,” Mr. Wicker wrote.