My guess is that there's nothing medically wrong with him.
I think he's just a bad person who isn't smart outside of music, so he's suggestible to movements that make him feel accepted.
The true nature of narcissism is defined by a deep and unshakable feeling of self-worthlessness. Deep down, they believe that they're not worthy of good treatment from anyone. So what they do to protect themselves from experiencing the pain of that worthless feeling is they put up this huge facade that basically say in so many words, "I'm the best! I'm the best!"
Their only other option is to wallow in their misery, and that's just too painful because the self-worthlessness is too deeply ingrained.