Dr Ryan Cole has suggested that a possible reason that the flu virus "went away" the past year is from arbitrium in the study of social virology. Viruses communicate with each other and suppress each other. For example, the cold and flu virus alternate in dominance each year. The dominant virus can trigger the genes of the less dominant to not activate. There is a cold and flu dominance through the decades history somewhere, I just haven't been able to find it yet.

A hypothesis is that the respiratory illness called Sars-Cov-2 is in the same struggle for dominance and actually could be shelved this cold or flu season, whichever becomes the dominant one. It's hard to say though when they're basically engineering a dominant strain from a massive, massive vaccination push. This is not a talked about subject though, so you won't find any easy reading on the subject if you do some digging and I don't fully quite understand it either.