When an Illinois judge sentenced Larry Hoover to up to 200 years in prison for murder in the 1970s, it was the sort of punishment that seemed destined to end his career as a Chicago gang leader.

But in the decades that followed, prosecutors said, Mr. Hoover’s power only grew as he directed one of Chicago’s most powerful gangs, the Gangster Disciples, from behind prison walls.

Young members would pledge allegiance to Mr. Hoover, whom they called their “king,” and those who broke Gangster Disciple rules, prosecutors said, would face bloody retribution “up to and including murder.” His influence continued to grow into the 1990s, when he was convicted of more crimes in federal court and shipped off to a supermax prison with a life sentence.

On Wednesday, after years of lobbying from Mr. Hoover’s supporters, including celebrities, President Trump fully commuted the federal sentence of Mr. Hoover, according to a White House official familiar with the matter.

The commutation was not likely to bring Mr. Hoover, who is now 74 and largely a memory in his hometown, back to Chicago’s streets. His state prison sentence remains in effect, with a projected parole date of 2062, when Mr. Hoover would be 111. But the president’s decision showed his willingness to extend leniency to some prisoners, despite his frequent rhetoric about the danger of violent criminal gangs.

Jennifer Bonjean, a lawyer for Mr. Hoover, said that the process to commute Mr. Hoover’s sentence had been years in the making. The entertainer Ye, who was formerly known as Kanye West, lobbied Mr. Trump during his first term in office, she said, and others have joined the effort since then.