> Mostly because the flu was somehow eradicated at the outset of mass covid testing (...)

Perhaps all those basic public health measures implemented to contain and eliminate the spread of air borne diseases such as COVID or the flu is a factor?

I mean,the lockdowns alone have a clear and critical and measurable (and measured) impact in lowering the spread of COVID. Wouldn't it be possible that staying away from people with the flu was also a factor in not catching the flu?