Wow, this makes me wonder if our understanding of capitalism is all wrong.

Capitalism is about amassing resources ahead of time and then trying to buy time, create a stalemate and wait it out until the other party has run out of resources and must give up.

Fighting a war accellerates the rate of capital exhaustion and destroys existing capital. Because everyone starts from a blank slate people do not have enough capital to waste on outwaiting their opponent and they instead focus on cooperation resulting in a few wonderful economic decades until everything goes bad again as people use their amassed capital to fight each other.