To me this description of cyclical catastrophe Explains so much - mud flood, missing people, missing history, undersea pyramids, etc. Although this document describes the future, it also explains the past.
THE ADAM AND EVE STORY | CIA FOIA (foia.cia.gov)

Here is the video that brought it to my attention:

Just a few days before, I came across this video...

The Next End of the World, CIA Declassified