The second half of Pepy II's ninety-four year reign was rather ineffective, as the forces that had been eroding the theoretical foundations of the Egyptian state became apparent. Since Egyptian kingship was based on the principal of divine kingship, a king whose economic power had been greatly weakened could no longer perform the role Egyptian doctrine had assigned him. "The consequences of this for the whole of Egyptian society were serious; the ex officio system of remuneration no longer functioned satisfactorily and the fiscal system was probably on the verge of collapse." (Shaw pg.116) There is no one reason behind the decline and ultimate collapse of the Old Kingdom and unified Egypt. From tracking the direction and magnitude of the Nile, experts have determined that this period in Egyptian history suffered an extremely low amount of flooding. Agriculture along the Nile was dependant upon annual overflowing so rich topsoil from upstream could be deposited onto the parched farmland. When this failed, Egypt's entire economic system failed with it.
As there could be no real warning before this catastrophe, any preparations would have been useless, and as a result, Egypt suffered a terrible famine. As easy as it may have seemed for nature to shatter Egypt into many independent city-states called nomes, it would never have happened had not Egyptian kingship been so heavily linked to religion. How could anyone cope with their god completely forsaking them? It may be that Egypt didn't suffer from an irreversible economic crisis, but rather a spiritual crisis from which they could not recover.
The reunification of Egypt didn't begin taking shape until the Middle Bronze Age. Two distinct empires arose from the ashes of the Old Kingdom. In Upper Egypt, there was Mentuhotep I's 11th Dynasty centered at Thebes, and in Lower Egypt, there was the great Herakleopolitan Empire which made up the 9th/10th Dynast.