The Nile valley was fertile soil  growing  rich and varied food

At the time of the building of the pyramids, the desert was not as extensive as it is today and the surrounding land most likely, would have been lush with vegetation.

The Nile river offered a navigation system to transport and trade goods as well as access to the ocean for trade

Egypt was surrounded by lesser civilizations who eventually became part of the Egyptian Empire

Egypt became a long standing power and the centre of civilization for several centuries