The king-men are at least sympathetic to the cause of the attacking Lamanites. This is perhaps an unusual situation that we need to examine. How is it that they expected that they would be in a better position if the Lamanites conquered the government of the Nephites? Once again the answer lies in the nature of conquest in Mesoamerica. The conquering army did not typically establish a physical presence, but rather extracted tribute. They tended to allow the local governments to continue to operate.
The king-men were those with the kind of lineage rank that the Lamanites would recognize, and they were certainly more sympathetic to the social structure of the Lamanites than were the faithful Nephites. Thus these king-men could refuse to defend Zarahemla because it would be to their advantage for it to fall, even to an enemy. The result could easily elevate their position and allow them to install their version of social order which is, in all likelihood, closer to that of the Lamanites.