Besides being a coke addict which probably included crack too(juding by some of his staments) he was also raised in Hollywoord so he thinks he is more special than anyoe else and entitled to everything.He’s been a star since his late teens early 20’s bessides being a son of a Hollywood legend.I doubt with his history that much of anything would get through to him and his ego.
Let's not get carried away. "Apocalypse Now" was Martin Sheen's only real "mega-movie." Most of his career was in made for TV tripe (he made a career of playing JFK.)
My favorite movie of his is "The Final Countdown" (1980.)