It must have been hard enough to build a pyramid in the first place, but to then completely take it apart?
It is, great post! Djedefre (elder son and successor of Khufu, although I don’t remember ever hearing that mentioned on *any* documentary, and I’ve seen a half dozen or few hundred) died not long into his reign, and his pyramid had barely begun. Something like 89 percent of the mass of a pyramid (other than, say, the Bent Pyramid, which is even heavier on the bottom) is found in the lower half of the structure, so if it took 20 years to build the Great Pyramid (for example), the first five years wouldn’t appear to accomplish much.
Uncle Djed’s pyramid (that was the nickname given to him by Menkaure, although I can’t substantiate that) was left unfinished and probably lost under the sands. In the 18th and 19th centuries it was used as a quarry, and camel-loads of masonry vanished into Cairo. The site is basically a big hole in the ground.
Why go to all the work of procuring new building materials when you can just use the stuff left over by that loser, what's his name, that preceded you?
Even easier. Just chisel out his name and put in yours.