Do viruses float freely in the air, or are they mostly in aerosolized bodily fluids when from an infected persons coughs and sneezes? Cloth masks are great at trapping those and greatly reducing the "muzzle velocity" of droplets that do escape.

Yes, this is the key insight. The mere fact that the virons are smaller than holes in the mask means nothing. The virons aren't expelled from our mouths or noses on their own, but are attached to moisture droplets which _are_ effectively trapped by surgical (and better) masks.

During mid covid I did a demo for my kids. A sheet of paper and a spray bottle.

Test 1, spray from 2 feet. Of course the paper was soaked.

Test 2, a cloth mask placed on the paper. It gets damp, especially if left in place.

Test 3, a cloth mask over the spray bottle. The mask blocks almost all of the spray.

We did not bother with test 4 (2 masks) after the 3rd, but I think they understood the point.

We did retry 3 with a medical mask, with 0 spray through.