Mormon has had to point to the Gadiantons as the ultimate destroyers of the Nephite nation (Helaman 2:13), even though they disappear after they are first introduced. Mormon makes certain that his readers know that these new Gadiantons follow the same secret oaths and covenants as the first band, but that these Gadiantons may not have been connected directly to the first. This is not a continuation of the same people, but of the same ideas. This is a continuation of the oaths and covenants that Alma wanted Helaman (the current Helaman’s father) to keep from the Nephite people.
Mormon makes certain that we know that Helaman (father of Helaman) was not the one to blame. If fact, it was no human who is to blame, but rather Satan, “that same being who did plot with Cain.”