As noted before, it is unlikely that all of the Nephites had left the land, and so this mission to the Lamanites was a mission to a different political unit, but quite likely to a number of people who had previously lived under Nephite rule and religion. Therefore this mission was not necessarily to “convert the heathen” but was still a form of a call to repentance. As Mormon notes, the success is centered in those who had been dissenters.
There are two types of dissenters that can be indicated in this verse. The first is the type of dissenter that we have seen creating the political havoc in Nephite government in the last fifty years of this history. Those dissenters were already rejecting the Nephite ideals and fomenting pressure for a change to the Lamanite system. It is difficult, though not impossible, for this type of dissenter to return. The problem is that they would already have had to make up their minds to separate, and justify that separation and subsequent rebellion or physical separation. Those who have actively decided to leave a religion may return, but it s a more difficult process than for those who had never known the religion before. It is therefore much more rare that such a person would return than that another type of person would convert to the religion.
The second type of dissenter that is the more likely target of Nephi’s preaching is the one whose dissent was one of convenience rather than conscience. This would be the great category of those who lived on the land and did not follow the political exodus of the Nephites to the land of Bountiful. These would be the people of the land, who throughout history have been more faithful to the land than to the vicissitudes of the governments that shift claims to their allegiance.