According to your reasoning, WW2 should not have existed at all, since it came on the heels of another devastating conflict. If anything, it's the post WW1 tha

According to your reasoning, WW2 should not have existed at all, since it came on the heels of another devastating conflict. If anything, it's the post WW1 that was taken as a lesson: instead of further afflicting the defeated, fomenting nationalism and isolationism, a more conciliatory path was taken. The union has its warts and boils, but the fact that the member nations have been at peace between themselves for the longest time span ever is hard to attribute to other factors.