That is a very reasonable question. (I hope that did not sound condescending). From the Woodward tapes, we know that he was aware this is an airborne disease, from the beginning. A national movement encouraging (not mandating) the wearing of facemasks only, would have saved over 50% of lives. We could have stayed working. And, with a few accommodations, most other activities would be only changed in minor ways. I have racked my pea-sized brain to try and understand why he did not take the lead in encouraging mask-wearing. The only answer is that it would not be a "slam dunk," and might tie him to other measures, like lockdowns, he hoped to avoid. And, he feared that if masks were not 100% effective, he would be seen as a failure. Fear is a horrible motivator. That is why we almost universally understand FDR's admonition, "The only thing we have to fear, is FEAR itself."