We see the Lamanites wisely and properly work to eliminate the main source of evil and wickedness among their people. Note that preaching "the word of God" is a very effective weapon in this war.
As this chapter opens, the righteous Lamanites preach to the wicked Nephites in Zarahemla, converting many. For a time the Nephites and Lamanites live together in peace and prosperity. The gadianton robbers guided by Satan, commit murders and all manner of wickedness and take over the Nephite government. This chapter provides insights about secret combinations.
Before this chapter is over we will see a rather complete switch between the Laminates and the Nephites. The Lamanites will become righteous and wise. The Nephites will become wicked and foolish.
To begin with, the Lamanites will preach the gospel to the Nephites and many will be converted. There will be a time of wonderful peace and prosperity for both the Nephites and the Lamanites but then there will be political assassinations .
The Gadianton robbers will gain strength and power. Then we see the beginning of the sad transition back toward wickedness. Many people will apostatize from the Church.
Perhaps you've noticed what is often referred to as the "Cycle of Apostasy" or "The Pride Cycle" in the Book of Mormon. We have seen it many times already, and will yet see it more times ahead. It is as follows almost every time the people become humble and repentant, they prosper. As they prosper, they become rich and after a time with wealth, they get prideful. Pride leads to wickedness, wickedness leads to destruction, destruction leads to humility, humility leads to repenting and keeping Gods commandments, which leads to prosperity and around the cycle they go again and again!
One of the major challenges as a people and as individuals is to avoid the cycle of apostasy. It can be done. People who remain humble and faithful despite prosperity are able to avoid going through the cycle repeatedly.
As we are told in this chapter, Satan is truly "the author of all sin". Verse 30 The Book of Mormon identifies a number of characteristics of secret combinations all of which are authored by Satan. The only way to destroy secret combinations is through preaching the word. (Helaman 6:37) (Helaman 6:26,29)
In verse 38, Moroni points out one of Satan's clear goals is to get people to truly believe that there is nothing wrong with sin and wickedness.
The Book of Mormon was written for our day. The Nephites never saw it, nor did the Lamanites. Mormon placed these events in the record for our benefit, in our own day. We may therefore expect that he knew we would face a similar situation and need to be warned. And indeed we do. The earth is ripening in iniquity again.