I think what they call "a thriving commercial economy" is very different to what I would call it; they won't be doing anything that sells anything that actually pays for what they are doing.
Competing for taxpayer funded contracts for things that are not commercially viable and don't make money and having a lower bid than others isn't the same as exploiting a commercial Lunar opportunity that supports itself. But once beyond Near Earth where satellites servicing Earth based customers are profitable activities taxpayer funded contracts are the only "commercial" opportunities. Without genuine opportunities for profitable enterprise - which the distance and difficulties prevent - I think there will be an enduring failure to thrive.
We can and will do many things in space that greatly benefit humanity - ie benefit people on Earth; without genuine commercial viability within the greater Earth economy (no such thing as an independent space economy) colonies on moon or Mars will require perpetual support and their innate and unavoidable failure to thrive independently will defeat any Longtermist "planet B" type objectives.
Asteroid minerals for Earth offers at least potential for self perpetuating growth on a commercial basis, whilst Meteor Defense is a shared security goal that does legitimately rely on taxpayer funding and can support ongoing taxpayer funded space technology development.
You are so far off the rails and have no understanding of what human frontier means. First and foremost, many of Mankind's industries will transplant to the space frontier (not Mars and not the Moon) for many commercial and environmental economic and societal reasons. Jobs and careers and lives will be opening up out there and emigration from the Earth will increase to where the industries, resources and the expanding energies and life will be. The only thing benefiting the Earth will be the synergy of the exchange of energies and filling the growing voids caused by a growing industry transfer and emigration out.
I cannot believe some people are so lacking in seeing the many, many, faceted picture of all history's expansionist frontiers of creativity, life and energy. Novas of so many creative frontiers, energy frontiers, growth frontiers, mind expanding frontiers, in frontier breakout from the equivalent of a growing black hole if it isn't done.
To begin with, what will be superconductively shooting down the chute to Earth will be products we might rather not make or grow on Earth but otherwise will be needed or wanted on Earth. Earth will be a new frontier benefiting from the unlimited growth frontier, Some just have no clue how things work, especially an opening system versus a closing system! There is no prosperity -- or survival -- to be had for humans on Earth doing nothing more than treading a treadmill to nowhere!
Out there, life and machine technologies will work together symbiotically like George Lucas, among others, imagined so well in his 'Star Wars' movies. Machines will not replace life out there, because artificial intelligence will be as varied as human intelligence, and in some, or in just as many cases, just as naturally complex, chaotic and stupid.