Why did US flu cases plummet US from 38 MM to less than 2k this season?

Everything we did against C-19. It (1) proves how effective masks, social distancing, etc. are and (2) C-19 highly transmissible compared to the Flu.

It's one more reason why the masks are never entirely going to go away.

I'm gonna go out on a wild limb here and say that masks probably had something to do with it (among other things).

that's a big change: can you share the source?