Conversation so far:
What did James Levine do with the opera?
James Levine was an opera conductor, most notably for the Metropolitan Opera in New York City
Was James Levine a singer or writer?
No; James Levine was a conductor and pianist
How long did James Levine work with them?
James Levine worked with the Metropolitan Opera for 40 years, from 1976-2016

Question: Why did he withdraw?
Self-contained rewrite: Why did James Levine withdraw?