Musk isn't going to Mars, nor does he care about any military applications of the technology. This is just an excuse for him to get more government contracts for promises he knows he will never have to actually fulfill.
Donald Trump knows the same thing, that we're not actually going to Mars. Like every President for the last several decades, he merely makes a promise of getting there that's so far out that everyone will have long forgotten said promise by the time the deadline arrives. Any President promising to do anything more than 8 years out is basically saying that it isn't going to happen. The next President will make the same "In 20/30/40 years we're going to Mars" promise. If you want to know the truth of the matter, just try holding your breath waiting for any of them to actually increase funding to NASA enough to make it actually happen.