Mormon does not tell us any particular reason for the prosperity—just that it happens. As a result of the prosperity, many join the church. “Prosperity” always denotes temporal prosperity, even if it is only as Mormon defines it. (See commentary accompanying Alma 1:31.) Acquiring temporal goods (wealth, costly apparel) nearly always included taking on worldly philosophies and ideas. This combination is the impetus to pride that violates the Nephite egalitarian ideal and begins to cause contention. In this case, however, I hypothesize that Mormon is recording only the early beginnings of this problem—acquiring goods but not yet importing their accompanying counter-gospel ideas.
As a matter of simple economics, the cessation of wars and contentions allowed the Nephites to concentrate on a healthy economy, thus leading to greater material prosperity. Although Mormon uses this period of prosperity to show the power of the gospel, from a more naturalistic view I hypothesize that, since the government and main religion were tightly intertwined, the Nephites saw this prosperity as a manifestation of Yahweh’s approval of both government and religion. Thus, for many, joining this Yahweh-approved church was simply a logical step.
Evidence that this particular mass conversion was shallow is the rapid deterioration into factions (vv. 33–34). Further evidence is that the conversions were so numerous that “even the high priests and the teachers” were surprised. Thus, the conversion was unexpected—not related to any specific effort on the part of the church.
These incomplete and perhaps improperly motivated conversions allow these same people to rapidly defect as conditions change. Within two generations, the church will become a persecuted minority.
Culture: The mention of “high priests and… teachers” confirms that the position of teacher in the church had continued from perhaps Nephi’s day. (See Alma, Part 1: Context, Chapter 2, “Alma’s Ecclesiastical Organization.”) A new development, however, is a plural number of high priests. Up to this point, only a single man at a time has been identified with that title; but apparently the church had grown to the point that it needed another level of organizational functioning. Because these individuals were “priests,” they therefore officiated. Assuming a continuation of the sacrifices of the law of Moses, these high priests were likely those in charge of the sacrifices. The multiple high priests were probably the ranking officials in each city, with the sacrificial functions being decentralized.