Pre-internet, if your misinformation came from the state, a biased news source, or your school teacher, it was much harder to find an alternative storyline, even if you question the truthfulness of something.
Now, I know folks are believing the misinformation, but to be fair, so many of us weren't taught how to sort out this stuff in school. The internet existed for me in high school, though we didn't have it at home save for a short time with dial up. My sister, 6 years younger, had internet most of the time she was in school and my brother, 11 years younger, had internet for most, if not all, of his teenage years. Schools hadn't updated curriculum all that much in no small part because the teachers weren't as internet savvy as the children. Attitudes ranged from "no internet sources" to "no wikipedia" but not so many restrictions outside of that. Entire generations of folks have had to just figure it out on their own, and some of us haven't taken the road of truth.