Rmases III of the XX Dynasty was probably the last great pharoe who tried to mainatain the esence and the pilars of the Egyptian Pharaonic world. But the World outside Egyptian had changed; new and young covilizations had emerged. Kinhs, hungry for victory, revenge or expanding their rules conquered the formal Egyptian Colonies eery where. In Nubia, Syria, Lybia or Greece new dyansties new kingdoms appeared that threatened directly the pharaonic civilization and even could control Egypt and declare themselves iinheritors of the Pharaoes.
You can get more information here.