As someone who has had the displeasure of talking to a few anti-vax people, I think it comes from a lack of understanding and the continued deterioration of trust in our institutions (government, healthcare, education, the sciences etc.).

The internet has brought a lot of good but also gave a huge population access to a bunch of unqualified podcast hosts to give them bad opinions. *cough* Joe Rogan *cough*.

What a shame, could've had a lot less deaths if people listened to qualified experts vs. any idiot with a mic and an audience.