The final phrase of this verse is important. Those Lamanites converted by the sons of Mosiah never fell away from the gospel. That is a remarkable statement. It is not a statement that can be made of the efforts of very many missionaries in the history of the world. What was the difference here?
One of the important things to remember is the vast distance that the Lamanites had to cross to believe in the Nephite gospel. They not only had to learn and love a new gospel, they had to learn and love a new God. They not only had to accept God, but they had to undo centuries of enculturation that taught them to hate the Nephites and anything Nephite. Under these circumstances, only those who powerfully felt the spirit would have any motivation to change. It is doubtful that there were social reasons why any of the Lamanites converted to the word of God. It is doubtful that any of them converted because their neighbors had. Each of them had to make an individual choice that was difficult, and could be made only through the compelling power of the Spirit. That great a change, with so great a manifestation of the Spirit is not only something not undertaken lightly, it is also unforgettable. At times it appears that the reward for the larger sacrifice to join the church is accompanied by an equally larger confirmation by the Spirit of the truth of that action.
Textual: The phrase “so sure as many as believed, or as many as were brought to the knowledge of the truth” is awkward. The presence of the “or” in the second clause indicates that perhaps the first clause was an error, and indeed it does not make much sense with the general direction of the verse. What cannot be discovered is whether or not this was an error in Mormon’s written text, or in Joseph’s oral dictation. Both are possibilities. It is the type of error that one expects of a dynamic situation where the formulation of the idea and the presentation occur in close proximity. That is, whoever the author might have been, they had conceived of the content of the paragraph, and begun a clause, then realized that the clause required correction. This is quite understandable in oral discourse. It is understandable in written text if the text is being written down as conceived. Since this does occur in Mormon’s historical narration, it is possible that he was writing on the plates without having created a copy beforehand.