The Metropolitan Opera fired the conductor James Levine on Monday evening March 12 2018, ending its association with a man who defined the company for more than four decades after an investigation found what the Met called credible evidence that Mr. Levine had engaged in “sexually abusive and harassing conduct.” It was an extraordinary fall from grace for a legendary maestro, whom many have considered the greatest American conductor since Leonard Bernstein. He made the Met’s orchestra into one of the finest in the world, led the Boston Symphony Orchestra and the Munich Philharmonic and gained worldwide renown through recordings, telecasts and videos. His fame transcended classical music: He shared the screen with Mickey Mouse in Disney’s “Fantasia 2000,” and made the cover of Time magazine in 1983, under a headline proclaiming him “America’s Top Maestro.” The Met said that its investigation, which was led by Robert J. Cleary, a partner at the Proskauer Rose law firm who was previously a United States attorney in New Jersey and Illinois, had determined that “any claims or rumors that members of the Met’s management or its board of directors engaged in a cover-up of information relating to these issues are completely unsubstantiated.” Since suffering a spinal injury in 2011 that caused him to miss two seasons, Mr. Levine has conducted from a wheelchair. It was only with great reluctance — and after a battle erupted behind the scenes when performers complained that it had grown difficult to follow his conducting — that Mr. Levine stepped down as music director in the spring of 2016. That year he acknowledged that he had Parkinson’s disease, which he had previously denied, and said that his difficulties on the podium were related to his medication.