> Why does this fear exist? I’m at a loss. Is it because people aren’t less educated now than they were 30 years ago? Is it because deadly diseases have fallen out of public consciousness? Was there a coordinated external effort to psyop the American people into believing such things (now I’m starting to feel like a conspiracy theorist)?

There was essentially a coordinated effort and it's not particularly a conspiracy. Shock Jocks, YouTube personalities, folks like Alex Jones etc all would gleefully share anti-vaccine sentiment because it got eyeballs and eyeballs is more money. Then it travels up the chain, creating an entire industry around anti-vaccine sentiment by selling snake oil. Eventually you get stupid enough politicians to genuinely believe it and enact policy on it.

And unfortunately most people are incredibly stupid with zero foresight. Someone's kid will die of measles and they'll just shrug and say it was God's plan. They'll gleefully send their kid with fifty preventable diseases out to die and kill others along the way.