It was always strict, that was its feature. But it was dying well before ChatGPT came along, due to going from strict to unusably over-moderated.

I'm all for a heavily moderated forum (that's why I like HN) but SO was clearly on the decline (from the graphs in this post) before LLMs came onto the scene. It peaked around 2017 (not counting COVID numbers) and was in a steady decline. ChatGPT just pushed it off the cliff (figuratively and literally).