At first Ralph celebrates when he realizes the absence of adults on the island. He exults in the sense of freedom he feels. As events transpire, he reaches the point when he desperately desires an adult presence to establish order and assume responsibility. Ironically, Ralph's disintegration mirrors that of adults who feel in control and then find themselves overwhelmed. Ralph's world on the island spins out of control, just as the world outside--run by supposedly powerful and capable adults--has also spun out of control, bringing the same results: savagery, destruction, and death.
As he goes throughout the novel, Ralph begins to be more and more concerned with personal hygiene, for starters. He notices himself and the other boys getting filthier by the day, and this stresses him out to the point where he can't concentrate. When his tribe decides to go meet Jack's tribe, he wants them to clean up as well as they can first, to put that noticeable difference between the clean boys and the savages.
Ralph relies more and more heavily on Piggy as the novel progresses, too. Ralph finds that he can't stay focused on his plan of keeping the fire lit unless Piggy is there to remind him of it. When Piggy dies, he is forced to think on his own, and he has a hard time doing it.
Ralph's leadership as Chief changes as well. He loses confidence when Jack's group breaks off of the main group, and he begins to fear making demands because he worries it will drive off the rest of the boys, or it won't work and his ineptitude as a leader will be obvious. He even begins to fear blowing the conch, in case no one comes.
In looking at the development of Ralph, my students often forget the first chapters of the book. Ralph is the one who stands on his head to make people laugh. He insists that his father will rescue them. He betrays Piggy just to impress the other boys. After becoming chief, Ralph struggles to become a true leader. When the littluns ask about the beast, Ralph simply yells at them that there is no beast. This does nothing to make the young ones feel safe or reassured. Jack is the one who offers them comfort by saying that if there is a beast, he will kill it. It isn't until after the fire goes out and the boys miss a chance at rescue that Ralph acts like a true leader; he makes rules that are in the best interest of the group, regardless of whether these decisions make him popular.
I thought Ralphs slow progression into incompetency was relative to the inhuman, savage acts that was becoming known of the boys. As Ralph slowly becomes inadequate the boys also become less civilized and more unruly than ever until jack finally creates a new tribe in which tyranny and fear reign in his command. The boys break more and more boundaries where they murder both Simon and Piggy until they finally loose what little decency they still held and hunt Ralph and use horrible and barbaric means that were not even used on the pigs until they finally close in on him on the beach where Ralph spots an soldier who comments on their savagery. Ralph is then shook but sobs; he cries for the loss of innocence.
Ralph appears to go from being a confident leader to second-guessing himself and relying on Piggy to allow Ralph to muster confidence. I don't think that could do anything in the latter part of the novel without Piggy. By the end, he was actually helpless and was rescued by the soldiers just in the nick of time.