These passages should be read together because they are meant to provide a contrast. We have the contrast of the angry Amalickiah because of the defeat and the grateful Nephites for their victory. Mormon does not attribute the victory to Moroni here, though he clearly appreciates Moroni’s genius. Rather, Mormon highlights the most important aspect of the defensive preparations for the nature of the text he is writing. He notes that the people were righteous, and this righteousness resulted in the blessing from God.