Maybe it's a built in defense mechanism that Heaven uses to Change the Mandate when the corruption sets in. It does have a tendency to topple capstones from time to time.
Maybe that's why the capstone never seems to be there for all to see. It's a dream until it's set in place. Or perhaps those who dwell within the control stone are afraid to mount the pyramid for fear of being seen...without the mask.
Just abstracting nonsense out loud.
Isn't that what this thread is all about?