This description is a brief notation that parallels the events surrounding the conversion of the Anti-Nephi-Lehies. (see Alma 23:6-7). It is significant that this mass conversion of Lamanites resulted in the same basic response as the Anti-Nephi-Lehi conversion. In both cases there was a laying down of the weapons of war. As noted in the discussion of the Anti-Nephi-Lehies, this is most interesting given the comparison to the Nephites, who do not seem to lay down their weapons of war because of their religion.
As noted for the Anti-Nephi-Lehies, it is probable that we are seeing here a laying down of the Lamanite cult of war. They were giving up a competing religion, and one that emphasized war. Thus the laying down of the weapons becomes symbolic of the Lamanite rejection of the Lamanite religion, and their acceptance of Nephite religion. In this same way we should see the rejection of the tradition of the fathers. This is almost Nephite code for Lamanite ways and beliefs, and those are also dismissed. Mormon is telling us that these Lamanites rejected their cultural and religious heritage and adopted the Nephite religion.
What will be most interesting in this conversion is that there is no alteration of political association attached to this adoption of the Nephite ideals as there has been in the past. Even the Anti-Nephi-Lehies relocated to Nephite lands and become Nephite, even to the adoption of a new collective name (the people of Ammon).