Flu also had exponential death/age characteristic (whenever a new strain emerges)
Like your brain that also seem to follow exponential decay. May be a vaccine effect. Most victims of a very strong flue are very young as these never had a mild flu before and thus no cross immunity. I guess you mixed up yearly flue events and strong flu events.
What the paper says:: It is well accepted that older persons (aged over 45 to55 years of age) were spared in the 1918 A(H1N1)
Totally different characteristics than CoV-19
When will you once read a paper before you link it and comment on it???
Did you understand the term attack rate ???