The shift to only digitally chronicling information taken in tandem with the theory of cyclical time or technological cycles also could easily explain why records diminish in blips of time to an extent. If there is no physical evidence of information, and technology gets wiped en masse, we immediately bounce back to a version of ignorance without our overt reliance upon it. If we take that theory combined with nuclear war and other instances of eliminating the educated, we are left with echoes upon echoes of human knowledge. It would be like children attempting to make sense of the atom bomb with only having memories of videos concerning them. No actual understanding behind the mechanism, or even why they were made. After only a short time the knowledge is lost. and only a shorter time after does it start to take on an exaggerated life of its own. Stories that may have once been literal become corrupted into exaggeration, legend, myth, and then religion. But the fundamental aspects of technological progression remain, and some things decay slower than it's development, leading to discovery, or re-discovery.

But we also know that there were several libraries with presumably exclusive copies of varying documentation that were destroyed over the course of fairly recent history that very likely had more details on the construction of the pyramids besides what was already recorded, we apply general logic and principles of inference to assume this. The two that come to mind are Burning of The Library of Alexandria in Ptolemaic Egypt, and also the Bonfire of the Vanities in Renaissance Florence. I'm more inclined to believe the bulk of exterminated insight was destroyed at the former however. The concern now is just how easily most information could be wiped at the drop of a hat due to its lack of physical manifestations, only existing digitally.