Monsieur
There are many megalitic sites on this planet and they are a mystery. Some people have ideas about how it was done but everytime i see one of those shows about "this is how they did it" they cheat and are only partially successful. They'll drive an already completed item on a truck and then try to drag it on some rollers for a short distance and claim victory. We don't really know the answers i think it's a big fat mystery.