I wonder if being multiplanetary actually makes a civilization more vulnerable rather than less? The thing about nuclear war on Earth is that it's basically un

I wonder if being multiplanetary actually makes a civilization more vulnerable rather than less? The thing about nuclear war on Earth is that it's basically unwinnable because of mutually assured destruction, and the threat of nuclear winter. Even if you win, you lose. On the other hand, it might be a lot more possible for a civilization on one planet to win a nuclear war against a civilization on another planet. Same with bioweapons: on Earth it would be stupid to try to use an "enhanced" ebola or COVID or bird flu as a weapon because you'd infect your own people as well as your adversary. But if you're separated by a great distance, that's less of a concern. In a way, the "dark forest" interpretation is too optimistic. The assumption is that one species will always try to destroy another independent alien species if they find one. But I wonder if it's even worse among members of the /same/ species but different cultures that are separated by a great distance.