I'm not aware of what damages Trump alleges in the suit or if it has any merit at all. Being rich does not mean there is no damage or disqualify a person from restitution though. And holding public office or a government job doesn't disqualify a person from protecting their private interests, although I imagine it could make the case a lot more complicated.

Aside, using civil courts to attack opponents is certainly a problem, but in USA it favors the speaker a compared to a lot of other countries. In US the plaintiff has to prove the speech is false and for public figures that there was malice. Which in my opinion goes a bit too far and gives media corporations more power over politicians and other public matters. I think the public figure stipulation is reasonable and important to allow private citizens to discuss politicians and public matters so that's good, but I think there should be a counter to that which requires organizations reporting the news to have more duty to report truth and not mislead.