I think there's a lot of all sorts in celebrity; histrionic personalities, narcissistic personalities, and people who struggle with identity, abandonment and rejection. The business gives people something they need, and the more you need it, the more you'll fight to get it. It's a cut throat world, and sometimes it's kill or be killed, but adoration, admiration, worship, popularity, etc... is like a drug for some, and others a life-force.
It's worth pointing out however, that just because someone might have personality traits like this, it doesn't necessarily determine whether or not they're a twat. being a twat and having a personality disorder can be independent of each other.
I.e. You're always happiest in the job that suits your personality the most.