The harshness of the surrounding land kept Egypt stable. The boundary line between arable land and desert was absolute, so it was never possible to settle on the fringe. Dissatisfaction was stillborn because no was nowhere for the dissatisfied to go.
Early on, there developed a sphere of political influence over hundreds of small communities, so the urban revolution never got started. The ruler was a king and god, which short-circuiting a separation of powers model seen in other cultures. Additionally, Egypt is a homogeneous geography which works against the kind of vertical economy seen in Mesopotamia. Near Sumer, plain, steppe, and mountain produced a micro-economic climate that allowed human task differentiation which was fostered in a urban setting.