Notice the conceptual parallel between the reason for Helaman’s preaching tour and the reason that Alma took his sons on the mission to the Zoramites:
Alma 31:4-5
4 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.
5 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.
In both cases we have threats of dissention, and the solution is not a military presence, but rather a reassertion of the fundamental glue of Nephite society, religion. The dissensions were seen as religious even though they might be more readily seen as political in the modern world.
For Alma and now Helaman, the real cause of the “many little dissensions and disturbances” was the drifting away from true Nephite religious beliefs and toward the religious worldview of the surrounding Lamanites. Thus the cure would be that which most directly attacked the cause. Helaman preaches to cure the social unrest.