Comment by holowoodman

The mechanism that lead to this is imho that humanities generally do not have any more grounding in facts, logic or reality. Science, technology and (to some extent) medicine and mathematics are bound to describe existing phenomena that occur in nature. They do this by observation and experiments (except mathematics), proposing axioms and theory, and then bringing those into strict logical agreement. Humanities nowadays reject observation and experiments as biologism. Or they never had those, and always just proposed ideas to be discussed, like in philosophy. They also nowadays reject objective logic and proof in favour of subjective evaluations and a wholly individual-centered world view.

This decline of rigor in the humanities means that they no longer really teach logic, critical thinking, or any kind of reality-related ideas. What they do is arbitrary and therefore objectively pointless, except maybe to further some political or social goal. That those goals are mostly left-wing is imho just an accident, they could as well be promoting right-wing politics.

(In a similar manner, arts now reject their original goals of beauty, aesthetics, depictions of reality, mastery and entertainment. But that's less of a problem, because arts have always been even less important than humanities.)