> And there's also nothing to be gained from Mars in any reasonable time frame other than research.

There is the prestige of having your nation expand, while others don’t. It is hard for democratic states to maintain long-term goals because power changes hands every election cycle, but it's not impossible that a stable and developed authoritarian country like China could launch such a venture just to cement its status as the leading superpower. That is not to claim, of course, that that colony would be self-sustaining anytime soon.