There's lots of implicit assumptions or this would be a book, but remember that Musk has a rocket and wants to colonise Mars, and that Mars is so bad that it is currently 100% populated by robots.

For the billionaires without rockets, there's also a whole bunch of deserts conveniently filled with lots of silicon.

(Or as Mac(Format|World|User) put it sometime in the 90s when they were considering who might bail out Apple and suggested one of the middle east oil barrons, a "silly con").