It sounds so preposterous to people that they kneejerk reject it.

Also, people just don’t want to believe that they spent so many decades trusting their rulers and accepting the nonsense without question.

It also puts people in a weird position when their research leads them far away from the official narrative. You can’t go around waking everyone up to this stuff if they’re not ready to hear it, so you end up having to navigate these two realities simultaneously to function in society.