The end of the Gadiantons, at this time, resulted in the removal of this particular Gadianton gang. As with other iterations of the Gadiantons, their destruction only appears to finally be their downfall. They will return.
The Nephites continue to use the same tactics as we saw with Chief Captain Moroni. When he took prisoners, he allowed them the opportunity to gain their freedom through a covenant. In this case, the covenant was not that they would not fight, but that they converted to the Nephite religion, and covenanted with God.
Verse 6 declares that “thus they did put an end to all those wicked, and secret, and abominable combinations,” at least until they arise again, and in not too many years.