Why did Tushan Jing hire XL to stop XY from marrying FL?
According to the original novel and the drama, I think we need to understand Tushan Jing's choice from several aspects.
1. Because he realized that XY didn't really want FL. If marrying FL was what she wanted, he would sincerely bless her, even if he himself would be sad and heartbroken. But all signs show that she didn't really want to get married. Therefore, he wanted to help her solve this problem so that she wouldn't regret it in the future.
2. Why didn't he stop it? First, he was already married on the surface (although we all know that he was framed). Second, he thought he had lost the qualifications to fight for or to be together with XY.
3. Why did he hire XL to do it?
a. In fact, Tushan Jing didn't fully know the relationship between XL and XY. But he knew that XY used to go out with XL, thinking that she likes his company.
b. During the Qingshui Town period, XY had promised XL that she would do something as he asked, and Tushan Jing knew about it. XL had bargaining chips and could persuade XY.
c. Whether it was FFB or XL, they were all outside the power scope of FL and CX. He had many means to achieve the goal of preventing CY from getting married. But one point that needs to be emphasized here is that Tushan Jing always puts XY's benefits first. That's why he told XL to solve it before the wedding. However, he did not expect FFB to take the bride away on the wedding day, which left XY no way out and hurt her reputation. (Although XL himself does not want XY to marry FL, he takes this approach for his own benefit: he needs to split the alliance between CX and FL, which is good for Chenrong's army. )
Tushan Jing has always been a person who respects women and their reputation. Just as he discussed the engagement cancellation with FFYY, he knew that the world treats women harshly, so he tried every means to cancel the engagement decently and minimize the damage to FFYY's reputation. However, he did not expect that FFYY loves her own brother deeply and would marry him anyway to realize their plan.