It's probably because he's more of a cable guy than a basketball guy, but it could be that he was born into money rather than someone who had to work for it.
Either way, Dolan has looked bad in interactions with unhappy fans and former Knick greats (see: Charles Oakley), signed declining players to big-money contracts, and forced out several decent management personnel in favor of poor ones, leading many fans to determine he "sucks" as an owner.