If (1) SpaceX is the only organization actually able to launch at scale (vs. promising eventual launching at scale while burning through $billions), (2) the Big Money in space will be made with large constellations of internet/cellular communications satellites and orbital DC's, and (3) SpaceX is winding down the launch services that it provides to outside customers - then all of SpaceX's competition for the $$$ will be stuck on the ground, giving them a monopoly.
Eventually, anti-trust law and/or another competent launch provider might break that monopoly. But Elon's buddy Don will control the Justice Dept. for a couple more years. And even for the competent, ramping up launch is slow.
Anti trust is completely out of the question. There is plenty of competition that is already selling contracts even if the physical product doesn't exist yet.
So we must break up a monopoly because it delivers more value at a lower cost than its competitors?
There's nothing stopping other rocket companies from doing the same thing Musk is.