the currency for viruses is they want to be as transmissible as possible. From their sort of evolutionary perspective, they don't really care whether or not they're causing disease in you as long as you're going to transmit it. So if a virus can make more particles, it's probably going to do better. But if at some point, it's making so many particles, you know, replicating so much inside you that it's making you super, super sick, at that point, you might not go out. You might not go to a party. You might not go to work. Worst-case scenario - you might die. That can lead to this relationship between how severe the disease is and how transmissible it is such that when a disease gets too severe, it's not good for the virus anymore.

Variants evolve to be less dangerous (fact) so if this "variant" is worse it means only 1 thing...