Ralph is convinced that the boys need a chief to guide them.
Ralph does not want to be chief for the power. He just wants to keep the boys together and keep them safe. Ralph has trouble keeping the boys together from the beginning. He is chosen as chief because he is the one who blew the conch, but this does not imbue him with leadership skills.
You said Ralph was chief and you don’t give him time to think. Then when he says something you rush off, like, like–” (ch 1)
Ralph is not sure he is the one for the job. It is harder than he thought. When Ralph complains that no one listens to him, Simon says he’s the chief and he needs to tell them off. Ralph is a nominal chief only, and has no real authority.
“I was chief, and you were going to do what I said. You talk. But you can’t even build huts—then you go off hunting and let out the fire—” (ch 4)
Jack takes over as chief for the boys in his faction, reinforcing his power by randomly beating some of them. In either case, they lack direction. None of the boys is qualified or capable of being chief.
Ralph goes from the height of his power as chief in chapter 4 to the low point in chapter 5. In chapter 4, he berates Jack for allowing the fire to go out and then commands the boys to rebuild it. He stands in place and silently makes the boys build the fire three yards away. This turns out to be the best way for him to assert his chieftainship--better than anything he could have devised through planning.
Right after that, however, Ralph convenes a late-evening meeting. After laying down rules about the fire and sanitation, his democratic tendencies resurface, and he opens the meeting up for discussion of the beast. The lateness of the hour and the spooky talk cause the meeting to deteriorate. Jack capitalizes on the boys' fear and leads them away from the meeting into a wild, unruly scattering on the beach. Piggy urges Ralph to blow the conch to re-assemble the boys, but Ralph is afraid they won't come and that will spell the death of his role as chief.
He realizes at this point that he really has no ability to control the boys. He won't resort to force or scare tactics, and most of the boys aren't mature enough to respond to reason alone. Amidst his own fears and facing his failure, he says, "I ought to give up being chief." Piggy and Simon try to persuade him that he is the only alternative to Jack, and that he must remain chief in order to keep the vulnerable ones safe from Jack. Ralph evidently takes this to heart because he continues to assert his chieftainship to the very end, even at the confrontation at Castle Rock. But he never again regains the confidence in his own leadership that he had in chapter 4.