The Monica affair was one of the first symptoms.
In 2023, Stack Overflow had already started making unpopular pro-AI moderation decisions, and in 2024, they started mass banning everyone who deleted their questions and answers in protest. I don't think it's wholly incorrect to say "AI killed Stack Overflow" when the death blow came from crazy pro-AI decisions from the admin.
The title of this thread is "What AI did to stackoverflow in a graph." That's a narrative. At least before the mods change it.