You would think – but viruses don't necessarily become less deadly.

The virus wants to maximize transmissibility, and that might require trading off further against the host's health and increasing its death rate.

An example is Myxoma virus. It was intentionally introduced to pest Australian rabbit populations (to cull them) and studied.

After ~30 years of evolution, they found the dominant strain had a 70-95% death rate and left long-lasting lesions. Other strains with higher (~99%) and lower (~50%) death rates weren't as stable & prevalent.

Once a virus is transmitted (enough), what happens to the health of its host is irrelevant.

[1] https://www.sciencedirect.com/topics/immunology-and-microbio...