Evolution theory by itself doesn’t give us the ability to explain everything in a certain moment, but that’s only due to lack of knowledge on our part.

Consider that measles in itself comes originally from a animal but a mutation found itself be able to spread to humans. That, in and of itself, is the process of evolution.

So while it is not necessarily a useful lens to try to interpret a moment in time as many unknown factors are at play (for example the same gene that is important for mortality might also impact survival in certain environments, and therefore how contagious it could be), if we were to understand it’s history of every mutation that came and went, the environments it lived in, evolution theory would explain why the path looked like it did. And subsequently why it is like it is today.