Evolution cares more about reproduction than longevity. Each organism only needs to live long enough to create multiple copies of itself before it dies & the population will grow. In other words, killing the host doesn’t really matter in an evolutionary sense as long as the average host infects enough people before he dies. The fact that the new variants are so highly contagious is their greatest evolutionary achievement.

As a human, that means even with a (theoretically) lower morbidity rate, the virus can kill more of us simply by infecting a larger population.