This is what we'll be up against, if a vaccine against Covid is found.

[Archae]

7. Zealots become the way they believe for different reasons.

A few, (fortunately only a few,) actually develop a form of mental illness.
Paranoid schizophrenia is one.

Others have a particular experience, and that convinces the person they are correct, no matter how crazy the belief.
I knew a guy in a job I had decades ago, who was convinced Santa Claus was real.
Complete with flying sled, North Pole home, etc.
He had "Seen Santa in his sled on his roof!"
I asked the guy was it possible it was just a very vivid dream he had? (I've had some even weirder)
Nope, he was set in his belief.
Otherwise, he was normal.

Others read an article, or see a video on the Internet, and are "recruited" that way.

As to Kennedy?
I think it's the third one.