Your comment seems to implicitly assume that X has some ethical claim to the content they're monetizing, when in fact they're trying to monetize _others'_ content.
I'd imagine you are totally confused why they don't do this. If you aren't confused why, well then you have your answer for why X has a right to monetize it.
You seem to be depending on a whole lot of assumptions to get to your "XCancel/Nitter/etc shouldn't be allowed to exist" conclusion.