As everyone is saying, it was already down-trending before AI, and probably experts exchange traffic and whatever came before looks similar
Also not sure exactly when they added the huge popup[0] that covers the answer (maybe only in Europe as it's about cookies?) but that's definitely one of the things that made me default reach for other links instead of SO.
Those popups were a big contributor for me to stop using SO. I stopped updating my uBlock origin rules when LLMs became good enough. I am now using the free Kimi K2 model via Groq over CLI, which is much faster.