Geo-political: We learn that there was a difference between the conceptual land of Nephi and the areas where Lamanites lived. The land of Nephi ran from the east sea to the west. This tells us that the land of Nephi was under regional control, and that it was an extensive front. What we also learn is that there were Lamanites who lived north of the land of Nephi proper. These would not be officially part of the Lamanite hegemony, probably due to the fact that they did not have a major city.
Moroni’s removal of the Lamanites from the eastern territories would not have helped much if he did not fill in that territory with Nephites. What this tells us is that he intended to match the Lamanite line of control with a similar somewhat parallel line of Nephite control.