During the Northern Expedition, Xu Da repeatedly intended to let Yuan Shundi go. Why was Zhu Yuanzhang happy when he knew about it?

Zhu Yuanzhang didn't want to be charged with regicide, which might be unfavorable to his later act of claiming the emperor. Therefore, during the Northern Expedition in Xu Da, Zhu Yuanzhang was very satisfied with his actions of arresting Yuan Shundi and releasing Yuan Shundi for many times.

At the end of Yuan Dynasty, Zhu Yuanzhang uprising led to Xu Da's Northern Expedition. During the first Northern Expedition, it went well. Xu Da attacked the Yuan Dynasty in two ways with hundreds of thousands of troops. At that time, Xu Da only took the capital of the Yuan Dynasty, which is what we now call Beijing. At that time, Xu Da led the army to win one after another, and soon he came to the present Tongzhou area. Sure enough, Xu Da successfully captured most of the Yuan Dynasty, but at that time he let Yuan Shundi go. This is the first time that Xu Da has let Yuan Shundi go.

After Xu Da occupied most of Beijing, he began to attack the merchants of the Yuan Dynasty. This time, Xu Da surrounded the merchants. However, during the siege, due to too many loopholes in command, the siege was not completely surrounded, so Yuan Shundi escaped again. This is the second time that Xu Da has released Yuan Shundi. Of course, it is said that Xu Da can capture Yuan Shundi in many wars in the future, but every time Xu Da lets Yuan Shundi escape. Did Xu Da do this on purpose?

Zhu Yuanzhang was very satisfied with Xu Da's above behavior. Someone asked why? Don't catch Yuan Shundi, kill him, and then Zhu Yuanzhang ascended the throne, by the way, not saved a lot of things? At that time, people attached great importance to the legitimacy of the royal family. If Zhu Yuanzhang killed Yuan Shundi in the war, it would be tantamount to regicide, and it would lose people's hearts.