The extra baggage that is his dad seems to be the issue. Also, less of an issue, but his brother might be a package deal, and he isn't near the 'get' that he is.
Stewart had more off-mat things go wrong last season than anybody not named Sasso. None was his doing, mind you, but you have to respect that he is still a very young man with a dad that is essentially trying to live through him. He wasn't even allowed to process most of it because his dad can't keep his damn mouth shut.