They thought they could win because they thought they were the superior people. They each had superficial martial systems while prioritizing loyalty and zealotry. Anyone with a brain was meticulously rooted out and replaced with a goose stepper.
They thought our factories were less than their willpower. They just had to show us what real war was like and we'd falter. We didn't have the guts to prosecute a war to the end. They drank an industrial sized batch of koolaid and lost to math.