Earlier quoted context omitted.
> "Countries that trade with each other don't make war with each other." I'm pretty sure this was the prevailing thinking prior to World War 1. A large scale conflict would be so damaging on a human and economic level that most assumed the people in power would find away to stop a massive war from breaking out. Well, they were right about the first assumption, but very wrong about the second.
It's also why the EU was founded, and in that instance it worked great. European powers used to be constantly at war with each other, but in the last 70 years there was no large-scale war within Europe (except for Ukraine/Russia, both not in the EU), and war between EU states has become unthinkable.
There's plenty of good things from a moral perspective about power being diffused away from a hyperpower hegemon, but stability and peace have never been among the side effects.