To Orwell again, he knew people can be easily programmed to believe ANYTHING. All that's necessary is to keep them from thinking for themselves.
Hence the democrat elite's urgency to convert schools, colleges, and universities from places of education to centers of indoctrination.
In the resulting environment, we can't be surprised the sheeple will believe whatever they're told, no matter how ridiculous, no matter how hateful, no matter how inconsistent with whatever they were told the day before.