Surely the seating of Mosiah2 as the new king was filled with ceremony. The people had gathered for an occasion, and they had been given a spectacular occasion, with a new name for their people, and a new king to usher in the new covenant. That certainly provided the conditions for celebration. Mormon doesn’t mention them. Mormon doesn’t say much at all about the coronation. He simply indicates that Benjamin finished, made Mosiah2 the king, made sure there were teachers to reinforce the new covenant, and then everyone went home.
It continues to be an important social statement that they returned home “according to their families.” There continues to be an underlying kinship organization in Nephite society, probably underscoring the continued use of the lineages of the tribes of Lehi as an organizational structure, even while they were among the people of Zarahemla.
This information would have been the ending of the previous chapter according to modern thematic definitions of chapters. For Mormon, the testificatory Amen meant that the chapter ended, even though the event had not. Thus, here, and in other places, information that modern readers might think belonged in the previous chapter had to be added to the beginning of the next.