Blame it on the stupid hippies who marched in the 60s chanting ‘Hey hey ho ho Western Civ has got to go!’
...and the left-wing professors who put them up to it.
One thing that never gets enough attention was how rotten the academic world was (riddled with leftists) even before 1968. That was just the year that there was enough critical mass, mostly from the brainwashed students of these corrupt high school and college instructors, to overwhelm the whole thing.
A huge number of leftists got into the academy in the 1930s and 40s (including refugees from Europe, who were steeped in Socialism), and of course there was already that Deweyan progressivist current running through it.