We can easily imagine that the appointment of Amulon as king over Alma's people would be the worst possible thing for them.
The real question is why it was an acceptable proposition for the Lamanite army. Why do they post a man as king over a subject people when that man had stolen away the daughters of the Lamanites, and had only recently been united with them?
One possibility is language. It is possible that there was a language difference between the Nephites and the Lamanites, and that Amulon, as a man of Nephite descent, would have a better grasp of the native language.
This possibility, however, does not appear to be strong in the reconstruction of events as we have proposed them in this commentary. Assuming the departure of Mosiah and his people still left many Nephites in the city of Nephi, and that any language change was precipitated by the integration with the larger-numbered Mulekites in Zarahemla, the return of Limhi to this are would have brought back into contact people who already spoke the same language; the remnant Nephites who had become Lamanites and the returning Nephites-Limhites (who return in a short enough time that they certainly had not lost their native tongue).
A more likely scenario is much more complicated. The logical reason from Amulon as the king would be his knowledge of those people, and previous position of power over them. This would create a more ready transfer of allegiance since it was an attitude that once was present in the people. They had previously seen Amulon as a leader, where any Lamanite would have been not only "foreign" but an enemy. This advantage might have been outweighed if Amulon's allegiance to the Lamanites would have been in question.
The reason that there was no hesitance concerning the Amulonite allegiance probably deals with two aspects of the ancient culture.
The first is the strength of the oath, which we have seen operative in numerous examples in the Book of Mormon.
The second is the bond of kinship. Even though the daughters of the Lamanites had been stolen, they were still Lamanites, and the marriages were in place. By this time the Lamanite women had accepted their husbands, and therefore these marriages created kinship ties with the Lamanites. Kinship bonds are particularly important in the ancient world, and we are justified in presuming that they would be effective here as well.
Once the oath was taken, the combination of the fealty oath and the kinship tie through their wives would have made the Amulonites into "Lamanites." They had elected to be part of that political and cultural system, and therefore could be trusted to operate in the best interests of the Lamanites.
Textual: There is no chapter break at this point in the 1830 edition.