According to most U. S. state health department records the levels of influenza recorded during the 2020-2021 flu season and the 2021-2022 flu season, when Covid 19 surges occurred, the levels of infection by influenza was below the baseline. Even the national data from the CDC shows the same thing, but no explanation has come forward to explain this phenomenon.
As I recall my >50 years ago course on Virology there was less chance of the influenza virus spreading among humans with all the masking, separation, and isolating at home.
All research studies since 1990 have demonstrated that masking the public has no reducing effect on viral infections, perhaps because the holes in even the best facemasks are about 50 - 100 times larger than many viruses. As for social distancing and isolation at home, neither has been a successful strategy to reduce infections.
Have a look at this useful RG link.
Article Impact of COVID-19 outbreaks and interventions on influenza ...
According to the CDC and many state public health department websites, during the entire 2020-2021 flu season influenza remained below the baseline level in the U. S. In the 2021 - 2022 flu season influenza appeared from December until mid-January and suddenly dropped below the baseline when the omicron surge was declared. It is just too contrived to suggest that the Covid 19 virus could prevent infection by influenza. I suspect it is more likely that the rt-PCR test cannot discriminate between them.
John