one of the main contributors towards fanaticism is low self esteem. but with age, this may mellow.
Some people think they need this sort of fanatism to give themselves some sort of meaning in life; that's how they define themselves.
I concur. The fanaticism we are talking about here is more of hero-worshipping. Usuall, fanatics need guidance. A leader. They don't get it at home. They get it in fantasy element. I notice that if a young star makes his debut in a mass entertainer story, something about a young man going against establishment, he gets tremendous following. We saw that in other younger stars. People like to be assured that everything will be alright. This was what MGR brought, and he himself would have astonished at the level of fanaticism. In Hollywood, you don't have fans rivalry, or fans, Plus, the hero himself will forget that he has real talents...this will be the case of Rajini. He is a damned good actor, but no thanks to his fanatic fans, he resorted to make mass entertainers.