Mormon attributes these developments to Satan’s influence rather than to the social norms of cultures surrounding the Nephites. The difference may be only technical. Satan uses the world to tempt us.
Narrative: At the beginning of this cycle, the Nephites were united in a life-and-death struggle against the Gadiantons that included righteous pleas to Yahweh. Yahweh honored his commitment by granting them victory. Now, however, the Nephites have rapidly declined into accepting worldly values again and have, in only two short years, reached “a state of awful wickedness.” This awful wickedness will cause even further destruction among them.
Typologically, Mormon is teaching a lesson from history. Righteousness leads to prosperity and peace. Unrighteousness leads to destruction. At this particular time, Mormon emphasizes the destruction, which is at first social, but which will become physical when the Messiah comes.
For Mormon, even this descriptive history will be typological. This wickedness followed by tremendous destruction is a type of the final destruction of the wicked when the Triumphant Messiah returns at the end of the world. When the Atoning Messiah comes (and he comes soon in this narrative), he will physically destroy the wicked. When the Triumphant Messiah comes, he will also physically destroy the wicked.