Mormon explained the reason it was expedient that he should make a record upon plates. He said that God willed it because of the prayers of some who had gone before him, "who were the holy ones" (3 Ne. 5:14). These records were to be preserved through time. They were to be used as tools to bring others to Christ.
Because of their faith, God heard the words of their prayers, and preserved a record that would benefit their posterity. These "holy ones," like Enos, were promised that whatsoever thing they should ask of God, it should be given them. This is a promise always extended to those who are saved (Hel. 10:4-10; 2 Chron. 1:7; D&C 7:1-8). Their faith was unshaken, they knew how to pray and receive answers, and God covenanted with them that the records would be preserved (Enos 1:11-18).
The Gentiles were last, but now are first. Israel was first, and shall be last. The Gentiles are called as bearers of the record for the first part of this latter-day winding up scene, and the remnant will soon receive it. And not just the remnant upon this land, but "all the remnant of the seed of Jacob" shall be gathered in, and shall be restored to a knowledge of Christ (3 Ne. 5:23-26).