Genetic predisposition is only one aspect.
I believe people who get addicted to drugs/alcohol are severely lacking in life quality, social connection and more.
Possibly suffering from childhood trauma too.
Once your life is garbage, you try to escape it. You can do it with unhealthy food, videogames, or alcohol/drugs. These are all addictions.
@AlexBrown84 how did you cope with life when it was totally trash, you felt terrible, had nobody, 0 success, no joy in life, nothing to look forward to.
You lost all hope.
Perhaps you haven't been in such a situation yet, be grateful for that.