Why did SO traffic halve from it's maximum till the ChatGPT release date? Also, for a long time after initial release, ChatGPT was pretty much useless for codin

Why did SO traffic halve from it's maximum till the ChatGPT release date? Also, for a long time after initial release, ChatGPT was pretty much useless for coding questions. It only became more or less useful ~2 years ago. So there's about 4x decline from peak to explain with reasons that do not involve LLMs. What these could be?