Why the Rebbe is the last Rebbe and will (hopefully) be the Moshiach

A story took place around the Farbrengen table of the Tzemach Tzedek (the third Chabad Rebbe) he clarified “The Baal Shem Tov took all the Jewish and Kabbalistic wisdom until his time and took it to the next level, following him, the Alter Rebbe likewise took all of his wisdom and took it to the next level” then Rebbe was silent and Reb Hillel Paritcher who was in attendance said “and the Rebbe took it to the next level.”

So we see there was a progression in the understanding of Divinity.

And based on the Sefiros, we know the Rebbe (our Rebbe) was the level of Malchus, which incorporates all the previous wisdom – but unlike the previous levels that have a vantage point – has nothing but the truth.