The point is that public justifications are more important than actual motivations. Actual motivations can be enslaving other beings, ruling / mining an extra planet or just wanting to watch the universe burn. Motivations are already present because there are millions of motivations that map on to the same result - destruction of another group of living things. I'm pointing out that it's easy to find public justification as well.

It's also possible to do this unilaterally. China or any other country could also unilaterally decide to destroy another planet. And same possibility on the other side.