"...a pillar in the temple of My God..."
In my reading today I came across the following which may help explain Rev 3:12:
...when John first introduced the New Jerusalem in Rev 3:12 he spoke of believers in the New Jerusalem as "a pillar in the temple of My God." In the ancient Greek world, it was customary to place a pillar in a temple in order to honor a dignitary. Thus John is not in contradiction to the later statement omitting a Temple; rather, he may be implying that the New Jerusalem is something of a Temple itself. By comparison with all earthly Temples, including the Millennial Temple, the New Jerusalem is unique. Earthly Temples had restrictions, even for the righteous, and hid the Shekinah in an innermost chamber away from all human sight. The New Jerusalem is exceptional in that it has no such limitations, but goes beyond them just as an archetype exceeds the model. For example, in the New Jerusalem, God's bond-servants "shall see His face" (Rev 22:4). This clearly indicates a new access without the previous restrictions given in Exo 33:20: "You cannot see My face, for no man can see Me and live!" The text explains that the reason this is possible is because the New Jerusalem cannot be defiled from within by sin because there is no curse there (Rev 22:3), nor from without, since no unclean person can enter (Rev 21:27)...
(Jerusalem in Prophecy, Randall Price)
...when a tzaddik [righteous person] leaves a place, it leaves an impression. While he is in a city, he is its splendor and glory, and when he leaves it, so too does its splendor and glory leave. (Rashi)...We learn that the righteous person is the foundation of the world (Mishlei 10:25). They represent the pillars upon which the entire world stands, and even if mankind does not recognize and acknowledge this, Heaven does, and it is Heaven that calls the shots in history.
Though it is true that tzaddikim act as a form of atonement for the generation that survives them (Moed Katan 28a), nevertheless the loss leaves a gaping hole in the spiritual fabric of society, thereby endangering the world in general. Historically, something always seems to go wrong in a big way after the passing of a great Torah leader.
Rabbi Pinchas Winston