Answer: Pharaohs losing power.
Explanation: The decline of Ancient Egypt was caused by pharaohs losing power starting by the Battle of Actium where Octavian was victorious. It was from there that Alexander the Great would begin to take control of Egypt and become Pharaoh. This resulted in Egypt becoming a province of the Roman Empire and ending an empire during the Hellenistic period with the death of Cleopatra, (its last representative) before the loss of this battle.