The reason for Helaman’s preaching tour closely resembles the reason that Alma took his sons on the mission to the Zoramites:
Now the Nephites greatly feared that the Zoramites would enter into a correspondence with the Lamanites, and that it would be the means of great loss on the part of the Nephites.
And now, as the preaching of the word had a great tendency to lead the people to do that which was just—yea, it had had more powerful effect upon the minds of the people than the sword, or anything else, which had happened unto them—therefore Alma thought it was expedient that they should try the virtue of the word of God. (Alma 31:4–5)
In both cases, the solution to threatened dissent is not military but religious. Dissent was seen as religious despite its obvious political content. For Alma and now Helaman, the real cause of the “many little dissensions and disturbances” was drifting away from true Nephite faith and toward the religious worldview of the surrounding Lamanites. Thus, reconversion directly attacked the cause. Helaman preaches religion to cure social unrest.