Corihor is not in the king-list because he rebelled against his father’s line. The separation of Corihor moves him out of the homeland of his father and to another land named Nehor, a name that became infamous in Nephite history. While the story line that Moroni gives has him drawing “away many people,” that cannot be the whole story. There is no historical problem with the fission of ruling lines, but the establishment of a new city that can be virtually immediately more powerful than the original suggests that there is history afoot that is not told in the recorded story.
From a historical standpoint, we must remember that this is a story that is told from the unique perspective of the descent line of Jared. This not only creates the interesting non-naming of the brother of Jared, but it also emphasizes the Jared-line to the exclusion of everything else that was happening at the time. The separation of Corihor could have taken him to other peoples who already had an established city, and that strength would have been ample to move against his father.