I wonder how much of it is people generally ignorant of the world starting to read a little bit, maybe spurred by Insta or TikTok, and feeling very smart about ideas they'd never heard before such as "vaccinations cause autism". Then, when the rubber meets the road and they start seeing the sickness around them, they snap out of it.
That reminds me: I have to update my vaccinations, like tetanus, shingles, etc., before they are outlawed.