The conversion of Alma the Elder was the prize jewel of the family history of his descendants for the next 450 years:
Mormon was not a son of Ammaron, so that was the end of Alma’s line, which began with Alma’s conversion by Abinadi. As far as we know, Alma was Abinadi’s only direct convert. He may have thought he was a failure. He had no idea how far and wide his influence would extend.
Likewise, Noah had no idea the effect Abinadi’s testimony would have on the Nephite people. Abinadi’s testimony was the great warning to all the rest of the Nephites and to the whole world as well. If we are not meticulous in keeping the law, if we are not faithful, looking forward to the coming of Christ, we will not have claim to blessings any more than Noah and his people.
The Book of Mormon is what Professor John Sorenson and the archaeologists have called a lineage history. What we are really being told from this point on is the history of the lineage of this man, Alma the Elder. The creation account of that lineage begins with Abinadi. It has a second phase, and that is with the conversion of Alma the younger, and those two stories will combine to be the main characteristics of this lineage. That is a great lesson on planting the seeds when you have no idea how the crop will eventually be harvested.
This is Alma the Elder’s equivalent of Paul’s road to Damascus. For the Nephite people, this beginning was what Latter-day Saints might understand as a Sacred Grove experience—a foundational spiritual event that moved forward God’s purposes among the people.
John W. Welch and Greg Welch, "Life Spans of Alma’s Lineage," in Charting the Book of Mormon: Visual Aids for Personal Study and Teaching (Provo, UT: FARMS, 1999), chart 28.