He was a kid that lost his "dad" and some scumbag seduced him with money and women. It's easy to see that if he stayed focused, the potential for greatness was there. He won the unified HW title at 20, was a physical force, and when he was under good coaching, showed fine technique as well.
Even if it was just simple choice like you're saying, your assertion that he was never that good is way off. That's like saying that Jon Jones was never a great MMA fighter because he can't stop partying. Jon may never achieve the greatness he could have, but he was still the best fighter by an order of magnitude in his heyday, and so was Tyson.