I think any of us; if we were raised within the context of Hollywood stardom for our entire lives, knowing no other frame of reference, then found ourselves with more money than we knew what to do with and were surrounded - again, from birth - by those who kept telling us we're special and super-awesome; I think we might have some trouble conducting ourselves in healthy ways, too.
Where do any of us expect that a man like this would have learned about humility, restraint, patience and respect? Is anyone here honestly puzzled about the cause behind the pathologically house-sized ego?
More profoundly, would anyone here be honestly surprised if it came to light that this and pretty much all other celeb meltdowns were as much entertainment and career engineering than just the idle efforts of a sensationalist media? (More information regarding celebs-gone-wild comes directly from the celebs and their publicists than you know. Being unburdened of a sense of shame; exploiting and promoting yourself by being "caught on camera" in various compromising positions is perfectly viable. Heck, it is actually necessary if this is the type of brand or image you wish to establish, for whatever reason.)