The failure of EDO is pretty remarkable. First time I've ever seen an expansion crater a game's playerbase.
An ongoing analysis of Steam's player numbers, seeing what's been played the most.
steamcharts.com
I saw that with Star Trek online Delta rising expansion. The stuff was bad, not in the "buggy" bad like EDO, but in the "we don't have any content to show so we make it grindy to make it feel like there is a lot to do".
Big drama, forum get a 15m between post rule, the Lead designer of the time post on Reddit (quoting) the people who complain are "entitled brats", which put oil on the fire. The CM comes and say (quoting) "the expansion is a success, and the player love it", spreading Baghdad Bob memes all over the place.
And as if that wasn't enough, they also nerfed the XP grind people where doing. Because it was not grindy enough.
Steamcharts went down fast. The expansion peaked about half what the previous one did (the all time peak player). But the previous one (their first) was actually very good.
Eventually, NCsoft took the CM as scapegoat and fired him. Poor guy was on vacation, he get back to being fired for following orders.
Fires died down over time, and STO continued its way into more monetization and grind. Oh and gamblebox. It's a star trek themed casino nowadays.
According to steam charts, the game is slowly going down, but not fast.
You also have the infamous "Star wars galaxy NGE", which kinda killed the game, but according to the devs, it was dying already, just more slowly.
And in the news nowadays we have Blizzard, who do their best to jump from one scandal to the next. And apparently WoW is suffering. I have my doubt it's going to kill it though.