You're missing how a bunch of their friends from their new social class already do drugs and how good those drugs feel.
Easy hole to fall into, but money honestly makes it harder to climb out of, you can always afford the drugs.
So it becomes the norm, whereas someone at the poverty line with an addiction can't afford them regularly and has to spend grocery money on them and therefore might be addicted but also resents them.
Rich people can afford to normalize drugs and consider themselves fine while they're on them, because they're still living within their means.
That's a ferret.