It’s pretty simple, actually. As one only gets tenure by publishing, and since only original “research” gets published, the Humanities would cease to exist if their professors confined themselves to things like “evidence” and “reason.” Shakespeare, after all, isn’t around to write any more sonnets, and we’ve long ago examined all probable causes of big historical events like the Civil War. The only thing to do, then, is entirely decouple the Humanities from reason and evidence. This is Postmodernism, and it’s so successful because it starts with an impossibility — it’s a fact, the PoMos declare, that there’s no such thing as a fact.
“Search your feelings. You know it to be true.”