I don't think whoever it was's vision of a trillion people in space has a snowball's chance in hell of becoming reality though. I think it's highly unlikely that the majority of humans will ever live anywhere but Earth, and if I'm right about that, there are few opportunities to make space profitable that aren't based on selling services to people on Earth. Of course the dystopian possibility is space simply gets weaponized (yay Space Force!) and the product we get is death from above.
As I noted on the previous page, there's a lot more of "space" than there is of "Earth." Like,
really a lot, even just in this solar system. This means that if we figure out how to live in space, it's essentially inevitable over a sufficiently long timespan that most of us will live there.
I think you're mistaking the problem for its solution. The fact that there is so much space (between everything of value) is the
problem.
Life is easy on Earth because everything we need to survive is highly concentrated in a place where there's also abundant energy. There's no other place like that, so life anywhere but on earth will comparatively be a struggle for resources you need to survive, let alone grow a civilization. The moon? Not enough volatiles. Maybe we can have some small settlements on the poles. Everywhere else on the moon there's nothing you'd want but rock and while you can live on rock you can't make living things out of it. Mars can provide a lot more, but it's never going to have an atmosphere so you'll be stuck living underground. Can it be done? Yeah, but
anybody who can scrape together the savings is going to head for Earth, which is a relative utopia.
The only reason for mining in space is to build things in space. It's never going to be cheaper to produce anything out there than it is to produce something good enough on Earth, so while asteroid mining might exist, it won't be for us here. It won't be a profitable exercise but instead a necessity to make things that cost too much to bring up from Earth. Almost anywhere but Earth and Mars the price of everything will be in delta V, which means water that has to be burned away into the vacuum. On the moon, the price of everything will be in water, nitrogen, and carbon.