Redaction: One of the subthemes that Mormon continually presses is the economic advantage of living the gospel. Rather than simply tell us that things returned to normal, Mormon makes sure that we understand that they also returned to prosperity. The foundational promise of the Nephites was:
2 Nephi 1:20
20 … Inasmuch as ye shall keep my commandments ye shall prosper in the land; but inasmuch as ye will not keep my commandments ye shall be cut off from my presence. (note also the negative formulation of this in Omni 1:6).
The resolution of the wars demonstrated the protection of the people, but Mormon must also make sure that we understand that God also kept his promise concerning the ability of the people to prosper in the land. Mormon presents the people at this point in time as repentant, and as joining the church. With that definition of righteousness, Mormon needs to let us know that God saw their efforts and fulfilled his part of the promise.