Jack and his tribe will give them food and protection from the beast.
piggy's glasses
Roger and Maurice are the ones that attack Jack and Piggy because Jack wants Piggy's glasses.
Well in chapter 10 Jack and his tribe of savages invade Ralph's tribe (made of up Ralph, Sam and Eric, Piggy, and one/two littluns) in order to steal Piggy's glasses, which is overall the power to start a fire on the island. Jack might have mentioned this plan in chapter 9 so I'm hoping this is the right answer to your question.
Ralph and Piggy participate in Jack's rituals because they are afraid of being excluded or targeted by Jack and his followers. They also hope that by participating, they can maintain a sense of order and control in the group.
Jack and his tribe.
ralph to piggy
Piggy concludes that Jack does not like him or Ralph, and sees them as obstacles to his authority and leadership on the island. He believes Jack views him and Ralph as weak and inferior to himself.
Ralph wants to get Piggy's specs back and Piggy wanted to kill Jack there and then.
The two people that jacked ordered to be captured were Ralph and Piggy
Ralph and Piggy develop personal-friend bonds, Ralph playfully teases Ralph while the other boys condescend him, Ralph is the only boy who defends Piggy however. Piggy stresses that Jack is against civility, which Ralph stands for, Piggy says that Jack holds no regard for Piggy, nor any concern for him.
Piggy is fully aware that Ralph is the only thing that is preventing Jack from becoming chief. Piggy knows that if Jack does become chief all hope of rescue will disappear because Jack will only bother about hunting and the signal fire wil be forgotten. Piggy is also fearful for his own safety.
Ralph respects Jack more than Piggy because Jack embodies strength, charisma, and hunting skills that Ralph admires. Piggy, on the other hand, is often seen as weak, unathletic, and reliant on others for survival. Additionally, Ralph and Jack share a similar leadership style and natural authority, making it easier for Ralph to respect Jack.