Yeah, SO's downfall started looong ago. The community was frankly horribly managed, and its strict "no remotely duplicate-esque questions ever" policy meant that answers to common questions just got more and more outdated as time went on. It's still common to search for something, find an SO thread, and find that the only answers are from 2013. The world has changed since 2013, answers in 2026 would be different, but because the question would be the same, any contemporary attempt at asking the same question would get marked as a duplicate, so the 2013 answer remains SO's only guidance forever.

They also had the problem that easy questions would get downvoted for being too easy, and hard questions would just not get answered because they weren't seen in time by the narrow group of people who could answer so they get buried by the algorithm. Working in something of a less common niche myself (embedded Linux), I never had questions get answered. I believe the question ranking systems and moderation policies really only worked for questions about new, popular web frameworks.

It was ChatGPT which did it in, but it could've been anything. It could've been a new group of people with some clout starting a fresh new knowledge site. People were ready to abandon SO.

It was also the rise of Github and the importance of the software hosted there. More consistent documentation and transparent issue trackers/PRs helped a lot dealing with evolving software.