People's opinion of the trustworthiness of authorities wasn't a blank slate when COVID began. Some people already believed (based on their life experience) that authorities are untrustworthy, and therefore chose to be skeptical of their claims during early COVID. Then examples of authorities lying about COVID/masks came out, which convinced those people that they were right all along. They'll be even more skeptical of the authorities next time.

That doesn't seem to explain how the "controversy" seemed to form almost perfectly along existing partisan lines in the United States, unless you're claiming that the baseline "trusthworthiness of authorities" was already divided as cleanly along those lines (which is not at all my impression). Moreover, I feel like preexisting "trusthworthiness of authorities" is very unlikely to be a good explanation for differences in views on vaccines, because I strongly suspect that people on all sides of these disagreements point to people they claim to be authorities in order to corroborate their views.

> That doesn't seem to explain how the "controversy" seemed to form almost perfectly along existing partisan lines in the United States

Awfully convenient, isn’t that?