Musk wasn't radicalized, he's always been this way. As the article says, SpaceX was founded with Michael D. Griffin, the head of Strategic Defense Initiative -- the very space weaponization program that Golden Dome is now modeled after. Griffin started the Mars Society with Zubrin (another war hawk), then took over NASA and funneled billions of dollars + people and plans to SpaceX before they had done anything.
The whole let's pretend to try and colonize Mars with private enterprise to help build the technology for SDI in plain view was conceived by https://en.wikipedia.org/wiki/Citizens%27_Advisory_Council_o...
(and indeed, lots of them were Heritage Foundation people)