Then after the War to end all Wars, we went and had another one.
Again, for a historian it was quite predictable. Lead people to feel they have lost control of their country and destiny, people look for scapegoats, a charismatic leader captures the popular mood, and singles out that scapegoat. He talks in rhetoric that has no detail, and drums up anger and hatred.
Soon the masses start to move as one, without any logic driving their actions, and the whole becomes unstoppable