I think it’s a combination of multiple things but I’d say the biggest one was the popularity of the smart phone. Once everyone started being online 24/7 the internet became too impactful for companies to ignore. People who previously never or rarely got online now had massive influence.
Reddit in particular managed to cannibalize every forum. We used to have unique forums for every topic that were moderated in their own way. Now they’re all condensed to one platform. There’s a handful of mods (I think 6-8 last time I checked), who overlap the top 500 communities.
There’s also the element of money for Reddit. It’s clear bots and the DNC spend a lot to keep their message on the front page. Ghislaine Maxwell was a mod of World News and had a massively influential reddit account. Pretty much every right leaning subreddit is banned except r/Conservative.
Reddit was doomed the moment Aaron Schwartz died. He was the one who kept it a free speech platform. I knew the second fat people hate was banned the reason I liked the website was done. It was only interesting to me because I could read so many different opinions and viewpoints even if I disagreed with them. It’s still a treasure trove of information though.
Some platforms are simply too big. Google, Facebook, Twitter, etc are all basically monopolies that should’ve been smashed a long time ago. People aren’t going to switch because they’re simply too big.
As for Blizzard, well it was once a company of nerdy gamers and now it’s a huge corporation. I think most gaming is like that now. Overly sanitized to the point of stifling creativity. Too many cooks in the kitchen and no unique gameplay loops, too many suits running the companies purely off profit and not making good games.
If you told the people running Blizzard in 2004/2005 we’d have a $90 cash shop mount and be able to purchase gold they would’ve laughed in our faces.