Orwell wrote this in a letter in 1944:

"Everywhere the world movement seems to be in the direction of centralised economies which can be made to ‘work’ in an economic sense but which are not democratically organised and which tend to establish a caste system. With this go the horrors of emotional nationalism and a tendency to disbelieve in the existence of objective truth because all the facts have to fit in with the words and prophecies of some infallible fuhrer. Already history has in a sense ceased to exist, ie. there is no such thing as a history of our own times which could be universally accepted, and the exact sciences are endangered as soon as military necessity ceases to keep people up to the mark. Hitler can say that the Jews started the war, and if he survives that will become official history. He can’t say that two and two are five, because for the purposes of, say, ballistics they have to make four. But if the sort of world that I am afraid of arrives, a world of two or three great superstates which are unable to conquer one another, two and two could become five if the fuhrer wished it. That, so far as I can see, is the direction in which we are actually moving, though, of course, the process is reversible."

I get the impression from Orwell that he thinks of these issues in too much of a top-down way. “prophecies of some infallible fuhrer.” It’s easy to mentally resist the propaganda of the fuhrer and his henchmen. You just have to parrot the lines, you don’t have to believe it.[1]

But these issues have become internalized, not merely something that the Ministry of Truth or whatever says. I think the introduction to Eclipse of Reason explains it better (published 1947).

In general I think “Truth” died due to Hyperreality. (If I could read French. Or understand Postmodernism.) Orwell’s vision has become too simplistic. I don’t really understand why his memes are so popular. Although perhaps on a meta-level it could be understood.

[1] The propaganda in Animal Farm was mostly delivered through the henchmen who personally berated the animals and gaslit them. It’s harder to resist even that.