Love learning about words and ideas like "interregnum". It's uncomfortable to think of a global societal interregnum -- at what point we may be in it, where it will end up, and if things will be "better" on the other side.
I’m confused by this because Nietzsche died in 1900. Was it a prophecy? Or did you mean the 1800s?
Yes, silly me. He was talking about the times he saw around him (late 1800s) rather than prophesising. In Beyond Good and Evil he poses the open question "what sacred games shall we have to invent?". It was Freud and Jung who were possessed with visions of awful wars to fill the vacuum.