All of Helaman 12 is Mormon’s comment on the state of the Nephite people that he described at the end of Helaman 11. It is useful to remember two of the last verses:
"And in the eighty and second year they began again to forget the Lord their God. And in the eighty and third year they began to wax strong in iniquity. And in the eighty and fourth year they did not mend their ways. And it came to pass in the eighty and fifth year they did wax stronger and stronger in their pride, and in their wickedness; and thus they were ripening again for destruction." (Helaman 11:36–37)
This “wax[ing] stronger and stronger in their pride, and in their wickedness,” came after Mormon’s descriptions of the power of Nephi and Lehi as missionaries, and after the conversion of the Lamanites. It came after Nephi had returned to a wicked and Gadianton-led Nephite government, and, particularly, after Nephi miraculously, publicly, and accurately prophesies. It came after they had humbled themselves and asked Nephi to ease the drought and famine, which was lifted only after Nephi prayed.
After all of those witnesses, they nevertheless began to return to ways that led them away from Jehovah’s covenants rather than toward them. Although Mormon has been giving his readers a selected history, it was not a dispassionate task. These events might have been around four hundred years before his time, but he saw the same attitude of turning against God’s signs among his own people, and writing about it stirred him.
This chapter has Mormon interjecting his own moralistic commentary on the sad faithfulness of the Nephites about whom he is writing.