If you were a radiation hardened interstellar race, having a body able to withstand extreme radiation because you've been traveling in space and exposed to cosmic rays and other extreme radiation sources for many many generations, your DNA having a much larger proportion of cross-links, your DNA encoding many more double-strand DNA repair mechanisms and overall redundancy, and you wanted to colonize our star system and in particular Earth, but there were these annoying rodent brained hominids currently occupying it, what would be better than the convince them to depopulate themselves, convince them their energy source was toxic, and even possible convince them to have a nuclear war?