The 1918 lethal flu started out mild like typical flu. The common flu (and colds) spread easily and don't kill their hosts ... or often don't even make them ill enough to stay home. All the better to let their hosts get out and spread better. The strains that are LESS lethal are naturally selected.
In 1918 europe however, the sick soldier was often sicker (cold, nasty trenches, etc) and was therefore transported to hospitals by healthcare workers. The sicker you were, the more likely you were to get transported and spread the flu. The MORE severe (and thus more likely to be lethal) strains were naturally selected.
Ridley (the author of the column) is smart and quite humble (I've read books and other articles by him) -- he admits to making mistakes, unlike our "experts" and mass media.
There is some evidence that the response to Covid may be causing selection of more severe (and thus more likely to be lethal) strains with the health system as a vector.
**IF** this is a factor, encouraging people to go and get tested (not a problem if you believe masks are very effective), and making them afraid enough that they are driven to seek hospitals for treatment.
If we allowed the general population to get out, the less severe strains would win the selection race.
As Ridley points out, we don't KNOW that ... it is a possibility.
If we were a free society with lots people thinking and discussing their thoughts, very little censorship (either overt or through shaming) of possibly "crazy" ideas, past experience would suggest that better ideas being "naturally selected" would win out.
In our current culture, the expression of thoughts like this article is likely to get you labeled as a "dangerous crank" and possibly "cancelled", or at least shamed.
Respect for actual free speech and diviersity of thought/discussion as a prime cultural value once "naturally selected" the old territory between Mexico and Canada as "exceptional".
What is cancel culture and shaming selecting?