Because Yang Ke and Ye Xun had been changing souls before, Silly Three's words only gave him an inspiration, which made Ye Xun feel that Ke Yang's soul could be brought back by changing souls and regarded Ke Yang as a lock. Without the key, your soul will be locked out and unable to return to your side, so this is the only way to replace Ke Yang's soul with Ye Xun, so Ke Yang woke up.
This question is similar to the second one. You take Ke Yang's body as a lock, and then the only key is made of glutinous rice, and you eat it. If Ke Yang's soul was not lost at that time, it doesn't matter if the key was destroyed in his body, but if his soul was not in his body at that time, he could not enter his body like a lock without a key.
Ke Yang must have said that Ye Xun couldn't let go and which one didn't run away. The master said there was something harder to let go of than you. He's talking about Sam. You know, Sam's fervent pursuit all his life is to be able to travel freely in xx. I guess the closer he gets, the lower his rejection of possessing the body, and the more he can become a living person. However, isn't Ke Yang the best candidate? No one is closer than his son, and we must not miss this opportunity to survive.
Li Dan finally said that Sam had left, because Sam had been lurking in Li Dan's body from the beginning, but he was getting weaker and weaker. Finally, after Sam died, the lock was opened, the door could be opened, and Ye Xun could come back. At a shallow level, Sam is the last thing Ke Yangming can let go of, but at a deep level, it is Bai Yexun of Ke Yangming who can come back.