am skeptical whether musk can damage trump politically. which magnate\celebrity\etc has done so far?

Musk is richer and is more followed/more influential (especially among big swatches of the right wing) than any other celebrity. He's got twice the followers of any other person on Twitter, and far more reach than Trump has. I doubt very highly that too much of MAGA would unfollow Musk if instructed to - they'd probably tune in even more to watch the fight.

Trump can certainly attack Musk and perhaps hurt him, but unlike attacking someone like Tim Cook or Bezos or Zuckerberg that would cost him significantly among his own base. Musk can also counterattack in a way that would hurt Trump in his base that neither Cook or Bezos or Zuckerberg could, because Musk has high levels of trust and popularity among portions of the right wing (especially the very online right wing).

And perhaps more importantly, Musk can damage Trump politically by hurting his chances of getting the OBBB through Congress. Trump is uniquely vulnerable to "ordinary" politics right now, because this is perhaps the only time in the next four years that he actually needs something passed through Congress. The debt ceiling needs to be addressed, the tax cut expiration needs to be held off, and he needs a lot more money for ICE/border enforcement. If he can get the OBBB passed, he could happily spend the next four years ignoring Congress - but if it doesn't pass, he's going to have to keep working with them to get these things in other ways.