Megillas Esther ends with the posuk, “Mordechai was great in the generation, accepted by most of his brothers.”
Why only most of his brothers? Why not all? Rashi explains that some of the Sanhedrin separated from him because he was no longer the man that he used to be. Till that point he had headed the Sanhedrin, but now that he was spending so much time in affairs of state, he no longer learned as much as he used to. Even though what he did was correct – he was, in fact, obligated – he wasn’t the man he used to be, so some of the Sanhedrin separated from him.
This Shmuz introduces us to the primary importance of learning Torah and the effect that it has upon a person.