History/Text: Mormon describes the Nephites as being completely converted by the twenty-second year after the Messiah’s birth (v. 7). From Mormon’s perspective, this historical statement is required for his religious history. The foundational promise is that Yahweh would protect the Nephites if they were righteous. Mormon has just shown that the people have been protected, and therefore they were righteous.
While it is possible that this is exactly what happened, it seems more likely that Mormon is recording an idealized view of the Nephite society. What textual basis would allow Mormon to assert universal righteousness as a “fact?” Certainly his sources would contain no statistics describing the extent and degree of the people’s righteousness. He may have had a spiritual witness about their righteousness; such a possibility should not be discounted. However, only seven years later, their faithfulness will fail. It is hard to imagine that the conversion of the entire population could have been as complete and sincere as Mormon paints it, only to dissolve within the decade (3 Ne. 6:10).
In other words, the best explanation of this particular verse is that Mormon is not writing a history that follows modern rules of evidence, but a sacred history in which it was absolutely true that Yahweh preserved the people because they met the condition of righteousness. As Mormon constructs his narrative, this had to have been a true statement; but a more modern view of history is that the seeds of those ultimate divisions were already present, even in the euphoria of victory that united the people. They would flower when watered by prosperity.