I'm a huge fan of BABYLON 5, but I never knew that the real reason that Michael O'Hare left as the lead after the first season -- he had begun to show signs of schizophrenia during production.
Showrunner J. Michael Straczynski offered to shut down production while O'Hare received treatment, but O'Hare insisted on continuing the season, and then left the show -- while Straczynski help him get treatment, pay rent, etc. even after he'd left.
They kept it quiet to save his career, but he told Straczynski that he could tell the tale after he died. Michael O'Hare died in 2012, and here is the first interview where Straczynski tells the story.
I need to do a re-watch of this show.J. Michael Straczynski on Michael O'Hare's battle with mental illness - EMMYTVLEGENDS.ORG