How did Zhu Yuanzhang design Zhang Wuji to abdicate automatically?

Zhang Wuji went to Zhu Yuanzhang, but Zhu Yuanzhang drugged him. Zhu Yuanzhang deliberately tied Zhang Wuji up, and then asked Xu Da and Chang Yuchun to talk in the next room, so that Zhang Wuji could hear the conversation.

Zhu Yuanzhang and Xu Da Chang Yuchun negotiated to get rid of the traitor Han Liner. Zhang Wuji mistakenly thought that they were talking about themselves, and was disheartened and decided to abdicate.

Reason: Zhu Yuanzhang wanted to be emperor, but Zhang Wuji's prestige in religion was too high, even killing him would not help. Knowing Zhang Wuji's temper, he devised such a plan to let Zhang Wuji abdicate himself.

Extended information "Eternal Dragon Slayer" ending:

Zhao Min left the palace for love and followed Zhang Wuji to try to rescue Xie Xun. Under the witness of Wulin people, Xie Xun abolished Cheng Kun's martial arts, blinded Cheng Kun's eyes, and finally revealed his true colors.

Xie Xun took revenge and became a monk. Zhang Wuji led Zoroastrianism and repelled the attack of Yuan Army, only to be calculated when Zoroastrianism was about to pacify the world.

Zoroastrianism general Zhu Yuanzhang set a vicious trap to alienate Zhang Wuji from Xu Da and Chang Yuchun, which made Zhang Wuji completely disheartened and resigned as the founder of Zoroastrianism. From then on, Zhang Wuji had no nostalgia for his Jianghu career and insisted on going to Mongolia with Zhao Min.

References:

Baidu Encyclopedia-Eternal Dragon Slayer