The more Zero spoke, the more they began to understand that this is not just any story. They realized that this is reality and truth they cannot deny. They remembered the men dressed in black cloaks and strange tattoos all over the party during the night their parents died. They remembered Zero's father saying goodbye to him as if he were leaving or something. They also felt that the motive behind their parent's actions is reasonable since it's a general knowledge that at a certain age, cultivation becomes impossible or close to it, making it harder for one to progress. Those four men activated their true potentials during the warring times, at a late age, they had almost no room for improvement neither did they have time to improve themselves. Seeking a second chance at life is the most reasonable thing to do.