The steep drop post-AI is different and reflects the ability of LLMs to answer a large fraction of the sort of questions people would ask.

Yup, the fact that ChatGPT can give me answers instantly, without dismissing or XY'ing me, "why would you ever want to do that?", "why don't you just do <thing you've already mentioned you tried>", or "just google it", has almost completely removed my need for StackOverflow.