I concur that Hasbro is a/the big answer. The "50M or die" dictum and that WotC was being led by someone who wasn't a gamer (and instead came from boys toys) was not a great combination for an RPG maker. Especially when it drove unfriendly fan policies (a repeat of TSR's foot shooting, in many ways). Plus, IIRC, I read somewhere that when WotC was purchased, Magic and D&D were considered separate divisions -- had they not been, Magic alone would've carried the division, and WotC could've let 4e's modest (by comparison) revenue continue indefinitively, and let passion rule the day rather than "profits".