One theory I saw proffered was that the blocks of the Pyramids were fitted on four sides with curved attachments that made it possible for them to be rolled (rather than dragged) up the sides of the pyramid under construction, using ropes or cords.
The great pyramid is composed of 2.3 million stone blocks, which range from 2.5 to 70 tons each. It's almost the height of a 50 story building, and its base is 13 square acres.
The interior chambers and the grand gallery are composed of granite, which was quarried at Aswan, some five hundred miles away.
The building is oriented to within three 60ths of a degree from true north, and the whole structure is within one quarter inch of perfect square. That is a degree of precision we can't even match today.
People have believed for centuries that the dynastic Egyptians built the pyramids and other megalithic structures using nothing but simple hand tools and brute force, but there has never been any evidence to support that claim.
In fact, every attempt to demonstrate the validity of such claims has failed miserably. Also, the archeological record is completely devoid of the sort of artifacts that would prove such primitive tools and methods were employed in the building of these monuments. Yes, there are copper chisels and stone pounding balls by the thousands, but it's not possible to carve multi-ton stone blocks that are perfectly square, to a machine-like flatness within a few thousandths of an inch.
Obviously, some kind of technology was used to quarry, cut, dress, transport, and place the stones of these monuments, but to date, no one knows the answer to that question.
I personally believe that some pre-dynastic culture was responsible, but who they were is an even greater mystery.