The "History of Ming" records: "Sun Yin took the son of the palace as his own son. That is to say, Zhu Qizhen was not actually Empress Sun's own child. He was originally born to a palace maid, and at that time, in order to compete for the position of empress, the Sun clan took this son of the palace maid as his own son. In this way, since Empress Hu only bore two daughters to Emperor Xuanzong, Emperor Xuanzong asked Empress Hu to "let Xian" and give up the empress's position to Sun.
(Empress Sun stills)
Since Zhu Qizhen was not born to Empress Sun. At the time of the "change of the door", why did she agree to the practice of Cao Jixiang, Shi Heng and others, and let Zhu Qizhen seize the throne of Zhu Qiyu?
Of course, the answer to this question seems to be very simple, because although Zhu Qizhen may not be Empress Sun's biological son (whether it is or not, it is disputed for later generations), he is his own nominal son. Zhu Qiyu himself was not his own son, but the son of Wu Xianfei. When Empress Sun saw that someone was willing to support the reinstatement of her titular son, she naturally couldn't ask for it. So, of course, she won't have any objections.
However, things are not so simple. If we understand this issue in this way, it is obvious that we will underestimate Empress Sun.
In fact, in dealing with many things, Empress Sun did not completely rely on her own relatives and dislikes. Why?
First, after Zhu Qiyu was captured, she actively supported Zhu Qiyu as emperor.
When Zhu Qizhen was captured by the Wala army during the Tumu fort rebellion, there were two opinions in the imperial court at that time: one was to run south and move the capital to Nanjing. The other was to support Zhu Qiyu as emperor and stick to the city of Beijing. In fact, these two opinions were unwilling for Empress Sun to accept. In particular, the second opinion is not only very risky to stick to, but it is likely to be defeated in the hands of Vala. And even if the battle is won, the throne will fall into the hands of someone else's son and has nothing to do with himself.
However, Empress Sun was not so selfish, but firmly supported Zhu Qiyu as emperor and firmly held the city of Beijing. In doing so, she apparently considered the future and destiny of the country. This made Empress Sun have a very high demeanor.
(Zhu Qiyu stills)
Second, Zhu Qiyu imprisoned Zhu Qizhen in the Southern Palace, and Empress Sun did not interfere.
Of course, Empress Sun loved her son very much (even if it was only nominally), and during the capture of Zhu Qizhen, she repeatedly sent Zhu Qizhen cold clothes to express her love for Zhu Qizhen.
After Zhu Qizhen returned to China, Zhu Qiyu imprisoned Zhu Qizhen in the Nangong, locked the gate, and filled the lock with lead, leaving only a window to send food in and out. They also cut down all the trees around the Nangong and sent people to keep a close watch on them to prevent Zhu Qizhen from acting abnormally.
For this kind of encounter of her son, Empress Sun must have dissatisfaction in her heart. However, she did not show this dissatisfaction and did not protest to Zhu Qiyu.
If she really protests, it should play a role. After all, she was the empress dowager, nominally still Zhu Qiyu's mother-in-law, and Zhu Qiyu was still her standing. Therefore, Zhu Qiyu would definitely not listen to her.
However, Empress Sun understood that if Zhu Qiyu was the emperor, once Zhu Qizhen's life freedom was restored, even if Zhu Qizhen had no ambition, it was difficult to guarantee that no one with ulterior motives would use him and bring turmoil to the whole country. Therefore, she did not do anything to persuade Zhu Qiyu.
(Zhu Qizhen stills)
Third, Zhu Qiyu deposed Zhu Jianshen and established his own son, and Empress Sun did not object.
Zhu Qiyu not only imprisoned Zhu Qizhen in the Southern Palace, but also removed Zhu Jianshen from the position of crown prince and replaced his son with the title of crown prince. This was absolutely extremely unpleasant for Empress Sun. Because for Empress Sun, even if her son has no chance of taking the throne from now on, in the future, when her grandson becomes emperor, the throne is also in his own vein. However, Zhu Qiyu removed Zhu Jianshen from the position of crown prince, leaving her completely hopeless.
However, Empress Sun still did not express a different opinion.
From the above three things, it can be seen that Empress Sun is not exactly a "calf protector". Although she is a female stream, she still has a big picture view.
Then, since Empress Sun had a big picture view, why would she agree to Shi Heng, Cao Jixiang and others making "changes to seize the door"? In fact, Empress Sun's agreement to "change by taking the door" is also a manifestation of the overall situation.
Because at that time, Zhu Qiyu was already terminally ill, and at the same time, he had no heirs. At this time, if she did not support her son's reinstatement, the throne would be vacant (at that time, Empress Sun did not know that Yu Qian and others were ready to support Zhu Jianshen as crown prince again). Once suspended, the country is in turmoil. Therefore, Empress Sun agreed to restore Zhu Qizhen to the throne, which was also considered from the perspective of national stability.
Of course, this does not mean that we can artificially elevate Empress Sun. Her selfishness must have been there. Moreover, she agreed to the "speculative behavior" of Shi Heng, Zhu Youzhen, Cao Jixiang and others, which also caused yu Qian and other loyalists to be unjustly killed, and later the "Cao Shi Rebellion". In addition, in the future, the party struggle between the ministers of the Ming Dynasty can be said to have begun at this time. All this was unimaginable to Empress Sun.
(References: History of the Ming Dynasty, Ming Shilu)