This is the big one - Musk knows that if he convinces enough people, they will invest the billions / trillions necessary, making him stupendously rich.
But anyone investing in that is... not a good investor, to be politically correct, because what's the expected return on investment? Who are the customers? What is the monetization? Or bar that, how does it benefit humanity?
It's throwing money down the drain. If you're an investor and are considering this, consider investing in earth instead. Real projects with real benefits. There's enough money to fix hunger, poverty, housing, education, and everything. Enough money to buy and / or fund politicians to make the necessary changes.
Perhaps. But I can also see someone wanting to use their money to fund space exploration because it is more exciting.
As an aside, I strongly suspect that to solve the problems you think are more worthy, it isn't money that is the problem, but rather social, structural, cultural, and other issues mostly.
Trying to do billionaire space shit while there is extreme poverty is a dangerous game imo; but I guess flaunting their wealth hasn't had any consequences so far.