Rashi says that the cloud covered Moses so that he could prepare to commune with the Divine Presence.
Like Moses, every rabbi needs times to isolate himself and prepare himself spiritually for his role.
The rabbinic life is demanding. On view all the time, the rabbi needs moments to seclude himself from the public. When otherwise is he able to think, to pray, to sort his own life out?
His community – every community – is a hard taskmaster. “I wanted the rabbi and he wasn’t there!”… “I met the rabbi and his mind seemed somewhere else!”… “The rabbi had his tallit over his head and he wasn’t looking at the congregation!”… these are some of the accusations, and they’re highly unfair.
The rabbi is no good for his community (or his family, or himself) if he can’t occasionally hide away under a metaphorical cloud.