Could simon have prevented any of the deaths?

We must first understand what Simon represents in the novel. From the beginning, Golding develops Simon as a Christ-figure. Simon takes on many of the characteristics that Christ had. Simon does not say too much but when he does speak it is to reveal some sort of truth. He defends the weak (Piggy,littluns) and he prefers to think in solitude. Simon is the only boy who understands the nature of the Beast; he knows the beast lives within all the boys. So, it is fitting when Simon scrambles down the mountain to tell the boys the "good news" (The beast that they see is just a dead pilot), Simon is brutally killed. In trying to save the boys from themselves Simon is murdered. The boys were past saving at this point. He tries to save them even as they kill him. There was no saving these boys.