Law professor Steve Sanders documents the change pretty clearly in a recent CHE essay (I have linked to a non-paywalled version).  He attributes this change, in part, to the increasing number of academics (at least in the feebler disciplines) who have openly abandoned the idea that theirs is a Wissenschaft that aims to produce knowledge of truths about its subject-matter.  This strikes me as plausible, but one cannot discount the extent to which one of the two viable political parties in the United States has moved to the quasi-fascistic right.  The two feed off each other, of course.  If serious public universities in the United States want to survive, they had better rediscover the idea of "the Ivory Tower."  Universities exist to produce and disseminate knowledge; they do not exist to advocate for justice or equality.