Then you have not seen a lot of crazy ideas. The pyramids are mostly still there, they haven’t vanished. They are also made of easily-removable stones. The sphinx is one large carved solid rock. The claim is there was a second solid rock sphinx that was razed flat.
It’s the difference between claiming the actual fact that a previous London Bridge was disassembled and then reassembled in Arizona is a corresponding fact to the completely false idea that there was a second Mount Rushmore that they had to flatten to the ground so people could get a view of the first Mount Rushmore.
One is plausible (and true in that case). The other is ludicrous. It’s absolutely crazy.