Can someone explain to me why Xielian killed Qianqiu's father?

spoilers!!!




after prince an le put a sword through his wife back and stabbing the king, he ordered the state preceptor (xie lian) to kill all xianle people cus the prince of said people basically kill off his whole family. xie lian didn’t want another bloodbath to occur so he made it seem as if he was the one who killed the entire yong’an dynasty leaving lang qiqi as the sole survivor.