Comment by dreamcompiler

I think power sometimes leads to this kind of insecurity, but a bigger factor is that people with narcissistic personalities often succeed because ordinary people are unaccustomed to dealing with them. Narcissists often come off as unusually competent, confident, and intimidating. This leads normies to want to follow them and give them what they want.

Narcissists are always extremely insecure, usually because someone crushed their ego during childhood. (There also exist people with intact egos who are simply arrogant; I'm not talking about them. The arrogant are easy to distinguish from narcissists after you study them a bit.)

My point is that Zuck was probably very insecure before the creation of FB, and he became rich partially because he was an insecure narcissist.