Addiction is a lifelong disease.
Success does not make the disease go away.
Being on a better team does make the disease go away.
Having willpower does not make the disease go away permanently.
Changing environment, taking the right advice from medical professionals, putting yourself around the right people, cutting off access to substances (the hardest to do, especially with how easy they are to get, including alcohol), constantly making plans to avoid be around any type of addictive substance (again, alcohol is everywhere), all of these things help to treat the disease, but even in the very best situation most addicts relapse over and over again.
In terms of “demons” or some idea that his upbringing led to this, science is leaning much towards it being a genetic condition and way more common than you think. I’m sure that’s the reason why about 90% of the “bad character” college players aren’t drafted. Teams know guys in college are immature idiots...it’s the lifelong drug and alcohol dependency that you can’t fix.