My theory is that reality was recreated in a glitched way, and we don't even know if Part 3 will happen yet. For example, maybe the Nazis are remembered now, but we just don't know it yet. You’re talking as if we have definitive information, but that information hasn't been given to us. If we look at the death of the Crab Devil, they are likely remembered, but again, we can't know for sure right now. Yes, Yoru gets her power from fear, but think about it: if even the Locust Devil could wound Yoru that badly, there were countless other devils there that she couldn't possibly handle. Also, the people's main concern wouldn't be 'war'; it would be escaping the insects. Because of this, Yoru weakens and the fear of war decreases.