>Probably we'll never know for sure and the lesson that ought to resound through the ages is that war is crazy and the winners are those who are best at confining the mayhem to foreign fields. Which was the US in WWII, FWIW.

Yes, war is crazy for sure.

After having read as much as I could stomach of Mein Kampf, I can add another lesson.
If someone says malevolent and crazy things the default assumption should be that that person is evil and given the opportunity he'll try to put his evil ideas into practice.
Just about everything that he did was predictable given what he wrote in Mein Kampf.