The latter seems likely to me. I don’t understand how anyone thinks the blame for mutations lies solely or even mostly with the unvaccinated. Vaccines, distributed in a pandemic, are likely to cause immense selective pressure, and that is one of the reasons that the WHO originally planned on non-vaccine herd immunity when they wrote their respiratory pandemic game-plan prior to 2020.

I’m fully vaccinated, not anti-vax, and not an expert. This is just my understanding based on what I’ve read.