So you think its mostly just coincidence that 4 years after AI is introduced stack overflow is dead?

No, of course not coincidence. It's just that people didn't have an alternative until 2021-ish. Users hated SO for many years prior, but had nowhere to go other than small niche communities. When LLMs came into play, it was just the obvious choice.

In an alternate universe, where LLMs didn't exist, I bet you SO would be equally dead by this decade. Someone better, with healthier values and a more welcoming community, would come up and steal their lunch.