I believe the reason the trial was in unvaccinated people, was so that it would have a big enough signal to detect quickly. If you did the same trial with vaccinated subjects, it might still be making a 50% reduction in hospitalization, but it would take a lot longer to detect that. I don't think the idea is to only give it to the unvaccinated.
I'd love to talk to someone who refused to get vaccinated but gave their informed consent to participate in this trial.
Kind of boosts my personal theory is that a lot of vaccine hesitancy is driven by the fact that it's an injection and if it were a pill instead people would be more willing to take it.
Your theory is entirely possible. But I’d also like to point out that the study population was entirely Covid positive people with one or more risk factors. Presumably if you’re overweight, over 60, and have Covid you probably are willing to take more risks than before to improve your odds of not dying. Even the vaccine hesitant might accept that risk.