It's interesting to watch how stories transform over time.
Twenty years ago, vaccine hesitancy was a story that well-intentioned researchers who developed vaccines which worked at preventing the illnesses but had the accidental effect of sometimes causing autism. To the extent there was a villain in the story it was corporate greed — ok, I have witnessed corporate greed, that happens. No one gets rich proving a vaccine shouldn't be sold, so even scientific researchers who are doing their best, modern medicine is searching for cures not problems: too many people get hired looking at why we should use more drugs and too few get hired looking for reasons not to. This all feels real-world: there's no villains from a Batman comic book, just a few greedy people at the top of corporations and a lot of systemic problems, a lot of people doing their jobs in a market economy where businesses and jobs come from selling something and no one makes a living by not selling. It is reasonable to be suspicious; reasonable to demand more tests.
Over time the foundations of that origin story were eroded: scientists *did* do more research on autism and vaccines, money was spent; scientists could have gotten famous if they were the one that confirmed the suspected link, or you don't know their names if they find nothing interesting. The early studies turned out to be a mess. The found nothing interesting — no one made a name for themselves by proving a real link.
As the foundations eroded, the story changed: the corporations went from not realizing the vaccines caused autism (and not spending enough money to do enough research to catch all side effects) to actively maintaining a conspiracy. And then it gets weird: we went from a few corporate heads being greedy to entire fields being absolute monsters. Now all those scientists who seemed like they got into their jobs in medical research because maybe a wonder drug saved their sibling or because they loved science were somehow, unexplained, super-cooperating like no normal humans cooperate but cooperating for evil (cue Dr Evil laugh). All the drug companies are cooperating rather than turning on each other — it's a League of Evil. Now the story is as astonishingly large and very conscious conspiracy whose purpose is to do something like kill lots of people, or make a merely-usual amount of money (the drug companies make this kind of money over and over, anyone check what viagra or hair loss drugs bring in?) as part of a vast conspiracy that nets together scientists, politicians, and probably your personal family doctor. All of whom are out to more or less destroy humanity (wait, how does that make profits again?) with a vaccine that most of them seem to be taking — so the media, almost every last reporter, must be in on the conspiracy too. Everyone around you, all those smiling faces who went to nursing school, is a villain laughing themselves to bed at night.
It's run-away fear no longer connected to things deeper than memes — but repetition of something being dangerous gets into our heads.