That’s a great read! Fauci explains what facts he didn’t have at the time and why learning those facts changed his mind.
If Covid was only transmissible by people with symptoms, you could control spread by asking those people to stay home and everyone else is clear — no masks needed. If it’s impossible to know if you’re infectious without testing, masks make more of a difference. More effective ones are obviously better.
I certainly knew at the time that I was triaging masks because health care workers were more important than me. I still have a note on my fridge from February thanking me for donating some N95s I had from wildfire season. The trade off was pretty clear.