If someone gets an infectious disease, we don't judge them for having a weak immune system.
If someone becomes addicted to a substance, we shouldn't judge them for having a weak physical or psychiatric system.
Addiction is a disease and should be treated as such. All of the xA (Alcoholics/Narcotics/Gambling etc) Anonymous are fine communal assistance groups, but addiction is not about will power.
Also, I am thinking that coming from a POV where I don't have any addictive tendencies makes it all the more harder to put myself in the other persons shoes. Not being pious or getting on a high horse here - it is genuinely like someone who doesn't have ADHD or autism trying to understand what it is like for someone who does. Analogies like the above makes it easier to comprehend though.
Mental diseases, however, look to other people completely different compared to regular diseases. Some argue they are not diseases at all, since they may lack known biological / cellular component. This becomes more complicated in case when they do not seek treatment.
Are you mad? Nobody suddenly becomes 'addicted'. Addiction is something you do willfully and deliberately to yourself. Addiction is not a disease, it is a form of self-harm.
"Self-harm" you mentioned is a mental problem. Yes, none of these are like cancer and deadly at first, but they really can turn deadly if no one helps. It is hard for me to understand too, but I don't take anything for granted. We never know what would trigger all these. I am sure he didn't want to die at 35 and leave her 3 years old kid behind with his wife alone.