This should not come as a surprise, and it was largely predictable from the outset. The flu has a base reproduction number (R0) less than 2 ( https://www.vdh.virginia.gov/coronavirus/2020/12/07/covid-19... ). Covid has an R0 in the vicinity of 2.5 ( https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scena... ). In the meantime, public health measures like masking and distancing will work against both viruses. If…
Assuming that this is due to "masking and distancing" and the small difference in R0 is crude thinking. It's unlikely to be anything of the sort.
First, R0 is not a fixed constant. It varies by context and location, and we've seen influenza decline everywhere.
Second, R0 is an estimated value. There are big error bars on all of these estimates -- the overlap is far greater than the 0.5 you're using to claim causality.
Third, rhinovirus has not gone away (estimated R0 There's something far more interesting going on here, it is surprising, and it isn't a "conspiracy theory" to talk about it. It's science.
(FWIW, my current favored hypothesis is that the closure of schools, and possibly travel, significantly affected the spread of flu. Unlike Covid, kids are a significant vector of spread for influenza. It's one of those little facts about Covid that is...politically incorrect...to acknowledge right now. But I am speculating, and there are problems with this theory as well.)
[1] https://syndromictrends.com/metric/panel/rp/percent_positivi...
[2] https://www.medrxiv.org/content/10.1101/2020.02.04.20020404v...