Earlier quoted context omitted.
> stealing other countries' shit at gunpoint, which went out of fashion after WW2 It didn’t go out of fashion. Industrialization made wars of conquest unprofitable by 1890-1910 or so, and it took the world that long to get a clue. (Russia, notably, still hasn’t figured it out.) If you build one factory, you make money; if you build an army to steal your neighbor’s factory, most likely you both get zero factories.
You never start a war to gain some bombed-to-shit factories or barren deserts, you start wars to gain control of valuable land with resources and more easily defensible borders, get control of lucrative trade routes, and gain workers(slaves) and natural resources for your own factories. Of course, it's much easier and cheaper these days to use your intelligence services to stage a coup in that country so that your co…
Which tends to have effects similar to what you've described. Land that isn't near a potential threat can be invested in much more heavily. Borders are easier to defend, etc.
But improvement to existing resources tends to be more attractive to those with the most resources already.