Free Real Estate
When it comes to colonizing a different planet, there are many things to consider. The most important thing to understand is whether or not the planet in question is inhabited by anyone or anything that we shouldn’t interfere with for whatever reason.
It is safe to assume that at this point in time there are no other living creatures on Mars. And therefore Elon Musk is free to colonize it with however many people he likes in whatever way he likes… Not that he owns the planet or anything. It would be a nasty surprise to be greeted by a Mars martian all of sudden…