Joe DiMaggio was a self-centered, controlling jerk. Among many other things, he had an outspoken loathing for Simon and Garfunkel because of the line in “Mrs. Robinson,” which he took as a dismissal of him and his career. It was very late in his life that someone finally convinced him it was a mournful longing for the days when he was the greatest player in the game.
I have heard that Christopher Reeve was a real jerk to everyone who served him in any way, or was “beneath” him on the pecking order. He only became a saint after his accident.
Tobey Maguire turned into an egotistical snot when he got the lead in Spiderman - too good to acknowledge fans or give autographs, even in appropriate settings.