“Egyptians were good at organization if nothing else.”
Slavery works for a while—until the slaves get rebellion on their mind.
Giza workers were mostly farmers, not slaves. The only slaves were captives taken in battle.
Slaves didn’t build the monuments of Egypt. Religion was a factor in their construction. Work on the project—get eternal life in the world over the sun. Work on the pyramids also got you a tax deduction, best medical care on planet Earth at the time and all the Beer, meat, and food you could drink. I believe it accidentally caused Egyptians to think of themselves as one people rather than a collection of villages—a form of nationalism. The real wonder is in the organization of the manpower. Still many mysteries linked to Ancient Egypt.