This is a true rival, and they have the advantage in numbers.
Although he had teamed up with Edward for a while, it was clearly a thing of the past, and at this stage, there was no need to continue cooperating. Everyone knew that to survive, they would have to rely on their own methods.
Moreover, his direct use of a domineering contract to subjugate the Flying Serpent Demon, along with his killing of the other few people, clearly showed his resentment toward him.
The last time the team split, it might not have been because the others agreed with Edward's views, but simply because they did not want to side with him.
Recently, Edward also became aware of the function of the Red Crystal Ant Queen and, possessing Rose's special equipment, he might have the means to control the Ant Queen.
