Why would an established people such as the Mulekites allow Mosiah1 to come into their midst and become their king (Omni 1:19)? According to John Sorenson, it is difficult to interpret the extremely brief and one-side account we have in Omni 1:13-19 of the joining of Mosiah's group with the people of Zarahemla. The story from the Nephite side represents the event as not only peaceful but enthusiastically welcomed by the locals. From the point of view of some of the resident people, however, the transition may not have seemed so pleasant. The key reason why there was "great rejoicing among the people of Zarahemla; and also Zarahemla" (Omni 1:14) is said to be that Mosiah brought sacred records when they had none. The impressive fact of literacy itself could indeed have combined with possession of the mysterious sacred relics in Mosiah's possession--the plates of Nephi, the brass plates, Laban's sword, the Liahona--to confer an almost magical aura on Mosiah that validated his deserving the kingship. Besides, he may well have had the right of kingship by descent from the royal "Nephi" line among the original Nephites (Jacob 1:11); I doubt that he would have presumed to accept the kingship in Zarahemla--he was a sober man, not an opportunist--unless he qualified for the king role as a (the senior?) direct descendant of Nephi. Without a strong leadership mantle of such a sort, the people in his party might well not have accompanied him out of the land of Nephi, nor would he have had possession of the large plates, the official history of the kings (Omni 1:11; Words of Mormon 1:10). In terms of the Old World tradition of the Judahite fathers of the "Mulekites," while Mosiah was not of the preferred royal line through Judah, at least he had major appurtenances of kingship that Zarahemla lacked. Zarahemla had only two qualifications, his current chiefly role and descent from Mulek (Mosiah 25:2), who, though of Judah and a descendant of David, was never actually king of Judah. Those qualifications apparently were not enough to prevail against Mosiah's strengths. . . .
The initial political amalgamation reported in Omni seemingly did not lead to genuine cultural integration but masked a diversity in lifeways that sometimes came forth as conflict in beliefs and behavior. Non-Nephite ways seem to have kept bubbling up from beneath the ideal social and cultural surface depicted by the Nephite elite record keepers. After all, the descendants of the people of Zarahemla probably always constituted a majority of the people in the land of Zarahemla. [John Sorenson, "The Mulekites," F.A.R.M.S., pp. 16, 18] [See the commentary on Omni 1:12]