> this is a symptom of a problem that started 10-20 years ago.

... and that's right when social media gained majority adoption among US adults.

More like 25+ years ago. In the early 2000s you saw a lot of celebrities pushing vaccine fear because they read some book version of "doctors don't want you to know this one wierd fact" that made the best-seller list or another. I remember people arguing about it in college classes, and I graduated in 2003.