As with his father before him, Mosiah appears bent upon transferring the kingdom while he is still alive and apparently sufficiently capable to translate the plates for our Book of Ether.
Nevertheless, he may know that his end is coming, for Mormon reports his death in this same chapter (verse 46). For whatever reason Mosiah was ready to pass on the kingship, none of his sons were available to take the responsibility. The people continue to want a king, but there is now a difficult line of succession.