These people were traders (capitalists) and built an incredible city in the desert. This was enabled by extremely efficient water harvesting (like in Dune) and by being extremely difficult to get to, making armies starve and die of thirst en route. It could be defended with a small force.
Having been there, Petra is quite weird: we've all seen the facade of the Treasury in Indiana Jones, but there's nothing inside, just a tiny little hole. The working theory is that it was in fact just a mausoleum, and almost all the rock-carved structures are actually just tombs, with the city itself almost entirely lost to the mists of time.
Capitalism is not just about trading, this is an anachronism, maybe deepen your historical & concept research if you care about objectivity. Also see: equi-vocation: etymologically, calling things the same. Aka confusion. https://www.etymonline.com/word/equivocation
https://en.m.wikipedia.org/wiki/Petra
These people were traders (capitalists) and built an incredible city in the desert. This was enabled by extremely efficient water harvesting (like in Dune) and by being extremely difficult to get to, making armies starve and die of thirst en route. It could be defended with a small force.