Mormon’s “moral” in recounting these miraculous deliverances is not just to demonstrate how the Three Nephites were blessed. He stresses that, despite all resistance and persecution, they continued teaching the gospel. For Mormon, the most significant miracle they performed was that many were “converted unto the Lord.”
When Mormon refers to “the people of that generation,” it is not clear which generation he is referring to. Four hundred years—the text calls it four generations (3 Ne. 27:32)—have passed between the calling of the Three Nephites and Mormon’s writing, but he gives no time indications at all. Obviously those persecuting the Three Nephites were no longer believers, so it seems likely that Mormon is either referring to the third or fourth “generation” or, generally, to events in both.