It became as annoying as experts exchange the very thing it railed against!

What was annoying about it?

Often the answer to the question was simply wrong, as it answered a different question that nobody made. A lot of times you had to follow a maze of links to related questions, that may have an answer or may lead to a different one. The languages that it was most useful (due to bad ecosystem documentation) evolved in a rate way faster than SO could update their answers, so most of the answers on those were outdated...

There were more problems. And that's from the point of view of somebody coming from Google to find questions that already existed. Interacting there was another entire can of worms.

They SEOd their way into being a top search result by showing crawlers both questions and answers, but when you visited the answer would be paywalled

Stack Overflow’s moderation is overbearing and all, but that’s nowhere near at the same level as Expert Exchange’s baiting and switching

That despite their url's claim, they didn't actually have and sex change experts.

the gatekeeping, gaming the system, capricious moderation (e.g. flagged as duplicate), and general attitude led it to be quite an insufferable part of the internet. There was a meme about how the best way to get a response is to answer your own question in an obviously incorrect fashion, because people want to tell you why you're wrong rather than actively help.

Why do you think those people behave that way?

Unpaid labor finds a variety of impulses to satisfy

Memories of years ago on Stack Overflow, when it seemed like every single beginner python question was answered by one specific guy. And all his answers were streams of invective directed at the question's author. Whatever labor this guy was doing, he was clearly getting a lot of value in return by getting to yell at hapless beginners.

That doesn't seem like the kind of thing that's ever been allowed on Stack Overflow.

So? It is commonplace there. The comments are even worse.

I don't think it matters. Whether it was a fault of incentives or some intrinsic nature of people given the environment, it was rarely a pleasant experience. And this is one of the reasons it's fallen to LLM usage.

Nope. The main problem with expertsexchange was their SEO + paywall - they'd sneak into top Google hits by showing crawler full data, then present a paywall when actual human visits. (Have no idea why Google tolerated them btw...)

SO was never that bad, even with all their moderation policies, they had no paywalls.