What we're not taught are the methodical psychological operations implemented over decades on at least 2 or 3 generations that lead up to a situation where an entire country could be fooled or intimidated into allowing such horrors to occur.

If we were taught the causes and not the symptoms then I dare say history would be harder to repeat. Go read Mein Kampf, 1984, Brave New World, Animal Farm, it's all there. The methods are extremely simple, it's just the level of psychopathy in our ruling class that is hard for people to accept.