Sanhedrin as Sovereign Entity of Klal Yisrael

Rabbi Zweig addresses fundamental questions about the nature of Jewish governance and authority by examining the transformation of the 70 elders from Parshas Beha'aloscha. He opens with the puzzling question of why we use the mother's name rather than the father's name in mishebeirach prayers, when normally we use patrilineal identification. The standard answer - that paternity is only probable while maternity is certain - is problematic because Dovid HaMelech used his mother's name despite the Navi clearly stating that Yishai was his father. The shiur then explores Moshe Rabbeinu's crisis in our parsha. When Moshe declares he cannot be like a nursing mother to the Jewish people, Hashem (ה׳) responds by establishing 70 elders. But this presents difficulties: similar elders existed at Har Sinai, and if they died, why couldn't Moshe simply appoint new ones as before? What fundamental change occurred?