The golden age of SO was when all the important questions that have accumulated over decades were getting asked and answered. SO stabilized once that backlog got finished, and then started dying once people moved to github issues for project-specific questions. Chatgpt just replaced the last remaining type of questions ("plz do my work for me"), which arguably shouldn't have been getting asked in the first place.

The peak number of questions was in 2013, and they had roughly zero growth between 2013 & 2016. They were in decline long before LLMs were on the scene.