You’re an even bigger narcissist than I thought.
As Salamander pointed out, it was because of the secondary bacterial infections in the age of no antibiotics, and not the influenza itself.
Before it got YOINKED! from the interwebs, a virologist pointed out that the secondary infections were likely caused by opportunistic pathogens inherent to the mask fetish back then, too.
We’re not meant to perpetually rebreathe all the crud we breathe out.
/Same as it ever was...