Interestingly, Nephi begins his future history of the gentiles’ relationship to the savior with his own people. With the pain that Nephi certainly feels for the future of his people, he must certainly have asked “why?” Nephi could not have had the personal relationship with the Savior that he had, and not wonder at how his people could ever lose touch with that relationship. Having see that it would be true, he would then have asked why it would be allowed, and if there was no lasting good to come from the road Nephi has set before his people.
Imagine Nephi in his time, at the beginning of creating a society for his people, and with the prophetic and firm knowledge of his Messiah. Nephi begins his people as not simply a population, but a community of believers. He teaches them not only how to eat and survive, but how to partake of the fruit of the tree - to eat of a more spiritual food. With all of his understanding and attempts to lovingly teach what he knows (see 2 Nephi 25:23) he yet sees that in the future it will all come to an end.
While not explicitly stated, Nephi is here giving us the answer he received. This is the “why.” Nephi sees the future travails of his people in the light of the record he is writing. It is the power of the message that will be preserved that will intimately play a role in the coming of the gentiles to a knowledge of their Christ, and their relationship to him.
Therefore, as Nephi begins his future history of the gentile redemption, he begins with his own people. He begins with the contrast of the previous righteousness, the tremendous gifts of knowledge they will have had, with the future destruction of that people. Nephi’s point is that while the people may be destroyed, the experiences, the prayers, and the writings will continue, and the message of that righteousness will survive the destruction of the people.