Answer:
He witnessed the conquest of Jerusalem and the destruction of the Temple of Jerusalem by the Roman Army.
He was always defending Jewish oral law, promoted the prayer in the synagogue, the study of the Hebrew commandments and the reading of the Torah. The Torah (Pentateuch) is the sacred law written by Moshe Rabenu (Moses) upon receiving it on Mount Sinai as narrated in the biblical book of Exodus.
He considered that these activities were the minimum requirements for the Jewish people to continue to exist in exile, anywhere in the world. Also, the memory of the Temple would be kept and passed from generation to generation. These practices were the foundations of the New Judaism.
Thanks to his efforts and guidance, the spiritual authority of the new Judaism was entirely in the hands of the rabbis, experts in Torah and Jewish law and not in the hands of the priests of the Sadducee party.