After the group saw Muka regaining her composure and jumping down to the arena floor where the fighting was going, the rest followed her. They didn't know why, but with Quinn gone, there was always someone who would naturally next take charge, and all of them seemed to follow her.
Even if she was flustered at this moment, there would usually be a sense of air around her. A leader wasn't just who was strongest. Peter could have taken that role, but he wasn't one to order others or help them out, yet Muka felt more like one.
Maybe it was the fact that Muka was already a leader before. The group had done little to help so far though, when the shadow beast had come, the group was waiting for some order from her, but she said only a few words.
