Clearly a highly intelligent guy; but obviously torn by a horrific childhood and caught in his own vicious spiral of self-loating and personal destruction. Addiction is not somthing reserved for the weak and societys outcasts, although many believe that crap; It could happen to anyone, imagine your father shoved a needle into your arm at 17 or in my case also a childhood I would rather forget.
Thing is with heroin, cocaine and other drugs like meth is that it does not take years of practice to get addicted. It's from the first hit. It from the moment you try it and feel the drug corsing through your veigns. Perhaps the phisical dependance takes a few tries after but not long.
Once caught into the slavery it then is any excuse to keep doing them. Escape, Im in a spiral, e.t.c. anything to maintain the flow.
Alot of addicts stop trying to get help as they feel that they can "maintain" the addiction and that they have not yet hit rock bottom. Thing is, that the drugs blind them form actually seeing that they are at rock bottom already. They might be like this guy, knowingly doing harm, knowingly off the wagon but unable to break free from the phisical and psycoligical addiction.
But it is possible to get clean and off the drugs.