There were three strong leaders trying to help these rapidly failing people who had lost sight of their God.
Nephi2 and Lehi2, the sons of Helaman2, were dealing with the government and the spiritual affairs. Meanwhile, Moronihah, the son of the great spiritually focused military leader, chief captain Moroni, was doing what he could with the military situation. This noble son of a noble father “did preach many things unto the people because of their iniquity” (v. 14). Because of the preaching and prophesying of these great leaders and their dire situation (having been overtaken by the Lamanites), the Nephite people actually began to repent, “and inasmuch as they did repent they did begin to prosper” (v. 15).
In a somewhat startling moment of self-awareness, the Nephites came to their senses and acknowledged their sins, problems, and weaknesses. The Nephites became greatly afraid when “they began to remember the prophecies of Alma, and also the words of Mosiah,” as well as when “they saw that they had been a stiffnecked people, and that they had set at naught the commandments of God” (Helaman 4:21). Only when they repented could Moronihah “venture to lead them forth from place to place, and from city to city, even until they had regained the one-half” of what they had lost (Helaman 4:15–16).
Book of Mormon Central, “How Did the Nephites Become Weak in Such a Short Time? (Helaman 4:25),” KnoWhy 175 (August 29, 2016).