NEW YORK—Conductor James Levine, who ruled over the Metropolitan Opera for more than four decades before being eased aside when his health declined and then was fired for sexual improprieties, has died. He was 77. Levine died March 9 in Palm Springs, California, of natural causes, his physician of 17 years, Dr. Len Horovitz, said Wednesday. Levine made his Met debut in 1971 and became one of the signature artists in the company’s century-plus history, conducting 2,552 performances and ruling over its repertoire, orchestra, and singers as music or artistic director from 1976 until forced out by general manager Peter Gelb in 2016 due to Parkinson’s disease. Levine became music director emeritus and remained head of its young artists program but was suspended on Dec. 3, 2017, the day after conducting a Verdi “Requiem” in what turned out to be his final performance, after accounts in the New York Post …