The closing of the story emphasizes the successes that Alma and Amulek had. They had converted Zeezrom; they had converted many who had physically left Ammonihah. While those who left certainly felt the loss of homes and lands and perhaps friends, they would find out soon that leaving will also have saved their lives. Better the loss of their homes than of their lives.
In addition to those converted from Ammonihah, there were others in the land of Sidom who were converted. We do not learn why they had not already been converted. Perhaps they were believers in the general idea of the Nephite religion, but had not formally associated with this new concept of a church. Their baptism was not only for cleansing from sin, but was also a witness of their entry into the church.