Ask yourself: in what year did it become difficult to ask questions on Stack Overflow? 2014? 2016? 2018? 2020? Aggressive question-closing was part of their design from the very beginning. Their high barriers to question-asking was the cause of their rise, as their primary user was never question writers: it was Google, and anonymous Google users. The whole thing was an SEO play from start to finish.
It's fun to imagine that their aggressive moderation was the "real" cause of their decline. It feels so gratifying, doesn't it? Finally those assholes got their comeuppance, because of their bad behavior!
But that's not why they failed. They failed because SEO businesses can't survive when AI answers the question directly, without referring you any traffic.
(The same thing is happening to Wikipedia, BTW, which is also aggressively moderated.)