Yip, LLMs were the executioners but SO had already long since put itself on death row for exactly what you're mentioning. I think sites like FlipCode were in many ways the spiritual predecessor of SO, and the questions were more of a part of the community rather than the definition of it. People need to feel free to communicate for something like SO to be successful, and they'd turned themselves into an absurdly user-hostile site where it seemed like people were competing against each other to see who could find a reason to close questions, rather than looking for a reason to answer them.
The irony is they were constantly looking for reasons to mark a question as low quality, but the moderation efforts were themselves extremely low quality, like absurdly so. Things would be marked as dupes when they had no relationship whatsoever, completely inappropriate questions would be asked antagonistically like 'provide a minimal replicable code example' for an abstract/theoretic question, and stuff that stood a chance of fostering a healthy discussion was just randomly closed.
It's perhaps a good example of the dangers of using volunteer moderators. It just never works out, because doing a good job of moderating is a thankless, time consuming, and painful job. So you disproportionately end up with people doing it for power over others or some perception of status seeking. In either case, these are the last sort of people you want having any authority whatsoever over others.
A big part of the picture was that they'd gamified the heck out of it. Community moderation can work, somewhat, but I've never seen gamified moderation work. Gamification is the big killer of collaborative communities.