Brant Gardner writes that since Mosiah1 was made king in the land of Zarahemla, we might want to assume that he was also king in the land of Nephi, but that would be an unsupported assumption. In fact, strong inference may be made that Mosiah1 was not the king. In Jacob 1:11 we find that the kings of Nephi took upon themselves the name Nephi. Not only do we have Mosiah1 named as Mosiah (and not Nephi the X), but the tradition of naming the ruler of the people of Nephi after Nephi completely disappears from the Book of Mormon from this point on. The easiest explanation is that Mosiah1 was a prophet, but not the king. [Brant Gardner, "Book of Mormon Commentary," [http://www.highfiber.com/~nahualli/LDStopics/] Omni/ Omni1.htm, pp. 14-15]
“And They Were Led by Many Preachings and Prophesyings”
Why does Amaleki not make any reference to his father Abinadom when he notes Mosiah1's departure to the land of Zarahemla? He just says, "they departed out of the land into the wilderness, as many as would hearken unto the voice of the Lord" (Omni 1:13). Chronologically, Amaleki's father should have been part of that group (Omni 1:23 -- "I [Amaleki] was born in the days of Mosiah"). [Alan C. Miner, Personal Notes]
[Omni 1:13]: They Were Led by Many Preachings and Prophesyings:
If Mosiah1's group were led by "many preachings and prophesyings" (Omni 1:13), their apparent righteousness seems like a radical departure from the words of Abinadom, who was most probably part of the group. Abinadom said, "I know of no revelation save that which has been written, neither prophecy" (Omni 1:11). Perhaps Abinadom knew of prophecies, but these prophesies might have been made by Mosiah1, who wrote them down in the large plates. This would make Abinadom's statement very accurate. [Alan C. Miner, Personal Notes] [See the commentary on Omni 1:2]