1. Because he is the most intelligent boy on the island.
Piggy has shown from the beginning that he has the most intelligence out of all the boys on the island. When piggy wanted to blow the conch. Or having ideas of the huts for shelter and protection. Even the idea for a sundial because he wanted the boys to be able to tell time to know the time of day. This proves that he has the most knowledge out of all the boys and is more intelligent to help with their survival while on the island.
2. Piggy cares for the other kids more than others would for each other
From the very beginning when they find the conch Piggy wants to find out if there are other kids on the island and to have everyone be together and piggy always has the ideas of sticking together to be as a group.
3. Piggy is the most logical out of the boys
Piggy has shown to has the most common sense out of the boys and while all the kids are outside trying to hunt he is taking change of all the huts and the fire even though he can’t do very much labor he still is the closest to society and order of their old lives. Between the kids piggy still is the most civilized out of the boys and isn’t going