All I know for certain is that the CDC Flu map changes dramatically between 2019 and 2021. We all can speculate as to the cause, but the data, if the CDC is to be believed, is concrete. What it looks like at a glance is that we somehow cured the flu when we compare the 2019 map to the 2020 map. If that is the case I have two questions; “one - if we cured the flu in 2020 why didn’t we take a victory lap and two - why were we less effective at mitigating the flu season a year later, did we forget what we did the year before?”

https://www.cdc.gov/flu/weekly/usmap.htm