> While there were individuals who resisted this, the systems of government and the belief systems that drove the totalitarian states where unprecedentedly horrific.

World War 1 happened 2 decades earlier and wasn't totalitarian and was nearly as horrific (the combat itself was usually far more horrific than WW2). The legacy of humans has been constant war for centuries before that. Even reducing it to some 20th century political ideology is insufficient. Human history has long been a series of duelling nation states, religions, city states, war lords, tribes, etc.

The only thing that stopped wars was economic production trumped state expansion while becoming global creating strong interconnections between nation states... and technology (ie, nuclear weapons, total war economies) made the stakes of war too high. But again that's just what stopped or slowed down the bloodshed, not a sufficient explanation of why it kept happening.