So, we have the first covid variant, fresh out of the stable. It has a lot of animal payload which will kill you. Then everybody wears masks. Masks have proven useless for all pandemics, but it's what doctors know. A mask is only useful in surgery for a few hours, under controlled conditions, to stop the surgeon from sending spit balls into the patient.
Masks on a large scale are useless. Everybody talks louder, and the masks get saturated. Nobody will wear a mask at a party, and so, there was a lot of 'illegal' activity. Nothing is measured, so the doctors can say that things would have been worse without a mask mandate. Just like nasa will always say the ozone hole would have been bigger, no matter how big the stupid thing gets.
Everybody wearing masks is a huge change of environmental conditions. This kicks in evolution, to try to get around it. Suddenly, the first variant is dead, and we go onto new variants. These avoid the masks and go straight for the eyes, flying through the air.
A molecular shift, or a choice of a formerly obscure variant is the same thing. Again, if we were engineering, we would go for more attachment points, more reproduction, and longer flight times. This requires more oxygen protection.
Oxygen hits that virus like little bombs. Incoming O2 blows up a spike or creates a big crater. A few hits and the virus is dead. We need more gob, or more sacrificial molecules on the surface. However, any extra weight reduces the flight distance. We are quite constrained.
There is a tremendous advantage to shedding some of the animal proteins. That way, we have it lighter, more contagious, and more reproduction. That animal payload does nothing.
-- to be continued
Termination - I write these on the fly, solving as a I go. This is heading to a conclusion that I don't want to make obvious to the doctors and such. So, I'm stopping here.