On a psychological level based on what I've been reading lately it may have something to do with emotional validation and mirroring. It's a core need at some stage when growing up and it scars you for life if you don't get it as a kid.

LLMs are mirroring machines to the extreme, almost always agreeing with the user, always pretending to be interested in the same things, if you're writing sad things they get sad, etc. What you put in is what you get out and it can hit hard for people in a specific mental state. It's too easy to ignore that it's all completely insincere.

In a nutshell, abused people finally finding a safe space to come out of their shell. If would've been a better thing if most of them weren't going to predatory online providers to get their fix instead of using local models.