There's a few things going on here:

1) History has never not been controversial... except for that glorious shining 40 years between Watergate and 9-11 in which white people managed to convince other white people that racism had been solved. Even in the middle of that we had A People's History of the United States and Lies my Teacher Told me. During that period the party line on Reconstruction was "things were complicated but it all worked out fine, just fine" (it did not work out fine and "genocide is something Europeans used to do."

2) History has always been utilized to justify current politics. Edward Said's whole point was that Europeans only study other cultures to justify their sense of superiority and only apply the frames of other cultures for their "otherness." Wallerstein noted that in studying sociology or anthropology, the only cultures studied are "nulls" where the object under scrutiny is so primitive and disconnected from other cultures as to disregard all influence other than that of the researchers. First Gibbon then Toynbee then the Durants created a narrative that goes "Minoa, Greece, Rome, darkness, Enlightenment, culture" without noting that "Rome" decamped to Byzantium after Constantine, without noting that everything we know about the Romans and Greeks we know because the Arabs and Persians skipped that whole "darkness" bit and without noting that Sumeria predated Minoa by an easy thousand years. That's an uninterrupted stream of perspective from Gibbon's first publication in 1776 to the Durants' last in 1975.

3) Collegiate expenses suffered a historic expansion from 1992-2008 due to aggressive financialization and a glut of degree seekers from 2008 due to soft jobs conditions. They started experiencing historic contractions in 2017 when Trump came to office and forced out or discouraged foreign participation, the only demographic that pays full price in the US.

Worthy of note - Zinn taught poly sci, not history. Loewen taught high school. From a position of pedigree, Bill O'Reilly has more business writing history (BA, Marist University) than Shelby Foote (dropout, UNC Chapel Hill) Nikole Hannah-Jones has no credentials in history, but then, the most important historical document of the past few years was in the paper, not academia. WEB DuBois had more historical cred than the rest of these people combined and he, too, had to write in the paper, not academia because, frankly, his writings didn't support the predominant narrative.

Gibbon wrote about a Rome that was a thousand years dead and yet, over the past two hundred years, plenty of new perspectives have been shed. Paul Kriwaczek has shed new light on the Babylonians despite the fact that they've been gone for two thousand years. I think it's a decidedly "associate professor" take to presume that just because there are fewer tenure track history professorships available there will be less history studied. I think it's more accurate to say that there will be a less homogeneous narrative which, in my opinion, is a very good thing indeed.