AAA games got too big to fail, so they had to be made to appeal to everyone, even if that meant they no longer appealed to fans of previous franchise titles. You Just Can't Make A Game About Things Like Space Marines With Dudes As The Primary Target Audience Anymore, apparently!
Crunch had to die because even though every game everyone's ever loved was made under crunch, crunch is stressful, it's bad to work hard on making something good, so that had to go, so millions could be wasted on making unsuccessful games.
Then, all the studios had to get bought up and consolidated and then laid off—who could've seen that coming a mile away?
It's been such a bummer to watch an industry I once cherished for its incredible output in terms of both technology and entertainment die a slow decade-and-a-half-long death, but, here we are.