Aside from the direct and indirect functions that the Temple served, it was also the pinnacle of Jewish life, and its absence represents a basic flaw in the very fabric of the Jewish people.
We must remember that, of all of the spiritual and governmental institutions that arose in Israel throughout the generations, none achieved a comparable position of centrality in the life of the entire people.
The centers of learning that became more and more important to the Jewish people throughout the generations depended on a substantial connection with the Temple.
Not only the Temple service and the force of the historic events, but the Torah itself made the sole repository of religious authority "the priests and judges who will serve in those days," located in this specifically designated place, "the place which God will choose"—the house of His choice, the Temple.
The destruction of the Temple, therefore, deprived the Jewish people of the central axis about which the life of the people revolved and toward which all other life expressions were directed.
Since that time, the Jewish people lack that central axis needed to direct the religious life, the national life, and the very existence of the people as a national body.
Thus the destruction of the Temple was not only metaphysically but also historically and actually "the removal of the Shechinah" (the Divine Presence) from Israel ("exile of the Shechinah").
As long as the Temple exists, there is direction and significance to the flow of life and the direction of life.
Whatever the number of Jews in the diaspora, and whatever the political and material position of the Jews in Israel, as long as the Temple exists, the entire nation knows that "the Lord dwells in Zion," and for the life of the nation there is not only a center but also a direction: there is a beginning and an end in the structure of life.
–Rabbi Adin Steinsaltz
From “Destruction and Redemption,” in The Strife of the Spirit by Rabbi Adin Steinsaltz