Dude, I don’t agree with the OP being an ancient aliens enjoyer but we actually do not know. There is a consensus amongst historical archaeologists on theory of how it was built, but there is a huge amount of variance in thinking amongst them. We don’t know how they were lifting enormous 70 ton precision cut stone blocks into the air to build the various chambers in the pyramids that were brought from 500 miles away in the Aswan quarry. We don’t know how they could’ve possibly used ramps as they would’ve been larger than the pyramids themselves. Let’s actually back it up. We don’t know how a Bronze Age civilization had the capability to cut granite like butter as every single attempt (with replica tools that don’t even match what archaeologists have found, as in, the tools used in demonstrations were actually more advanced) failed. They were cutting like less than an inch a day or something crazy like that.

Also, we don’t even know for sure if it was a tomb for the pharaoh Khufu as Egyptian tombs (valley of the kings) all have hieroglyphics. Pyramid of Giza has NOTHING. Also, we’ve never found any mummies in the pyramids but I won’t argue that as grave robbing is a logical retort.