Moving asteroids or building telescopes doesn't get Musk investor money.
SpaceX has it's whole purpose as getting man to Mars, rocketry and satellites are the paving stones towards that. If he wanted to just get richer but do it in space, making factories, space stations and asteroid mining (with huge deposits of gold, platinum, rare earths etc) would be the prime focus. Setting up a colony on Mars, with a decent possibility that you will be dead by the time it has happened isn't a get rich scheme.
Be as cynical as you want, your choice. But I get where he is coming from as I'm similar in age. I was born in 68 (2 years older), grew up the tail end of Nasa's moon project, my first film that I went to see independently was Star Wars, I lived on a diet of space 1999, Buck Rodgers and the like, plus all the sci fi novels that I could get. The Apollo program was 50 years ago, I thought when I was young that as an adult I'd be flying around up in space shooting aliens, it is a disappointment that we haven't returned with boots on the Moon, let alone having an active base/colony/s. I'm not the only geek of my vintage with those disappointments.
Some people spend their spare dosh on a rare treat like an ice-cream. Some people have a bit more and buy a yacht or vacation house. The mega wealthy spend it on mega yachts. I think he just get's more meaning and purpose out of doing this than sipping cocktails on a mega yacht in the Mediterranean - not surprising given that he's studied physics.