Musk is already launching satellites for the DoD through SpaceX's Starshield division.
Hypersonic missiles might be a bit more offensive than what Musk is accustomed to, but for tens of billions of dollars, he will probably be happy to assist.
If anything, an orbital bombardment platform armed with conventional munitions would be more aligned with SpaceX's existing core competencies.
Musk can even frame it as an asymmetric remedy against the emergent long-range, precision strike capabilities of a certain unnamed peer and an easier to name near peer . . . Might even be cheaper than the NGAD program!