The Mittler Rebbe explains:
These sparks of Tohu that fell down into the worlds of BY”A became elevated to the level of the Name צְבָאוֹת, which is related to the elevation of the Keilim of BY”A and the multitudes of creations connected to them to Elokus. However, this is only the level of Malchus that descends into BY”A, into the Keilim of the Sefiros of BY”A, as explained above.
However, the Jewish people themselves were elevated by Moshe Rabeinu to his own level of Atzilus itself. Only the Eirev Rav remained on the level of BY”A, the regular Jewish people actually reached a level similar to Moshe, because of their strong connection to him.
In other words, when the Jewish people left Egypt, they weren’t only the “Army of Hashem,” they reached the level of prophets of Hashem, who experience Hashem directly and fully, just like in the world of Atzilus.
