They actually don't really know how they did it, there are the voices that say ramps would've been so enormous that they wouldn't have been practical in a realistic sense: https://www.cheops-pyramide.ch/khufu-pyramid/pyramid-theories.html There are supporters of the lever theory, even several different methods depending on the progress of the construction: https://en.wikipedia.org/wiki/Egyptian_pyramid_construction_techniques?wprov=sfla1 But as I understand it as a complete layman ( my only qualification would be that my ex girlfriend was an egyptoligist) that the more they examine it, the more voices raise against a solely ramp method. The old egyptian were highly pragmatic & efficient, so I've heard, and the stones were gigantic, sand ramps are at least partly unpredictable & sand is not the stiffest construction material - sooo, I don't really know & as far as I know, science doesn't either, at least no exhaustive answer. So far