I think you are assuming that being wealthy is just a state someone gets into magically.
While the things you mention aren't on their own crazy species changing ideas, the selling stuff, the getting a cab is what allowed some folks to become wealthy and go after crazy things. So don't discount the process of acquiring resources.
It's the means to the end. Nothing wrong with that either.
Bezos was being connected with space as the destination in the 90s long before Amazon was even a certain hit or Blue Horizon. Amazon gave him the means to follow his childhood dream. That's not to trivialise an Amazon, but had Amazon failed, which it almost did, whatever came next would try to get big enough to make Blue Horizon. Selling books online wasn't unique, getting big fast was more so, at least for a while.
For Musk, he'd identified as having a dream of alternative energy, solar, and electric vehicles from years ago and mentioning it along the way. No surprise that as soon as he can he's founding Tesla. With SpaceX right after Paypal I cant recall hearing earlier mention, but I'm glad he did.
Lots of people have wacky childhood dreams. Our society picks who gets to pursue theirs based on money. Some inherit it. Others execute magnificently on something daring.
For the latter, their dreams seem like good bets to bet on (but only given the prior performance). For the former, I suppose it's a plus they mostly remain in a holding pattern.
Oh but we do. Statistically such things contribute a lot more to humanity overall, it's just less visible because the benefits are widely distributed. What enables projects like this is the huge amounts of human labour that have been saved by less glamorous projects, along with general innovation in manufacturing.
We don't progress the species with digging up more rocks, building more stuff, selling more stuff, or dare I say it, finding a new way to get a cab.
A few more vastly wealthy eccentrics building teams to play with space, fusion (carefully I hope), generation, or whatever pipe dream they have could easily make up for some of the global short termism.
Does it matter if he sells enough tickets to Mars to profit? I doubt it. I don't think that's the point. The moon landings were excellent for helping humankind dream big, Mars will be too.
What will the moon landing conspiracy theorists do then? :)