[DiogenesKynikos]

If you read the scientific literature on masking (focused on a flu pandemic) from before the pandemic, there was actually a lot of uncertainty about whether masks would help the general public.

It's obvious that masks help if they're worn correctly, but the uncertainty was around the question of whether the general public would actually wear them properly. In hindsight, it seems obvious that mask-wearing should have been encouraged from day 1, but it somehow wasn't initially clear.

One problem, I think, might be the emphasis on controlled randomized trials (RCT) in medicine, which are not always appropriate. Think of running an RCT on whether parachutes prevent death when falling from planes. We understand the physical mechanism underlying parachutes, so we know mechanistically why they prevent death from falling. Covid is a respiratory virus. Masks physically filter the virus out of the air you breathe in and out. You don't need a study to know that if worn correctly, they will reduce transmission. The real question is how to teach and encourage the public to wear masks properly, not whether masks work in principle.