It is somewhat true, but the virus doesn't know that, and there isn't a strong evolutionary pressure to make covid less lethal. Covid is transmitted mostly dur

It is somewhat true, but the virus doesn't know that, and there isn't a strong evolutionary pressure to make covid less lethal. Covid is transmitted mostly during its mild phase, it only becomes severe a week later, if you are unlucky. If you are lucky, you clear off the infection and gain relatively strong immunity. For the virus, both scenarios are similar. The only thing is that if it was just a cold, we wouldn't bother with preventive measures and the virus would spread more easily. However, when both the lethal and nonlethal variants are present, the nonlethal variant doesn't have an advantage since we treat everyone the same way, so it is unlikely for the nonlethal variant to take over on its own. At least not on a short timescale. The solution is to create our own nonlethal variant, also known as a vaccine. Well, vaccines don't spread, I guess we could make a vaccine that spreads but "what could possibly go wrong..."