Gu Qingzhi/Shen Xihe single-handedly ended the entire 7 man strong heir apparent run. Like all the princes had a chance at the throne till she happened.
In her early form, she took out Changqing who was widely expected to ascend once the sickly crown prince died. She dies first round, his momentum dwindles and then 2nd round he forfeits magestically for her.
Everybody else has a theoretical chance but she realistically snuffs out that pipe dream, with heavy handed help from the crown prince himself.
The Crown Prince desperately wants to be Emperor and is doing everything to stay alive and ascend the throne and have a historically impressive reign! He falls fatally in love (in ways only Changqing can accurately explain) and all he does after that is prepare the kingdom for HER reign!
The total and quiet decimation of such a well stocked Princely generation could fit into a more malicious revenge themed drama with ease but instead Shen Xihe plays it out like a mildly thrilling chess game.
We must pay respect to the woman who pulls off the race to ascension with such grace and style, a femme fatally for the ages, the incomparable, beautiful and wise: Previously Prince Xin's Consort Gu Qingzhi, Di daughter of the illustrious Gu Clan; now the Di Daughter of the Military Shen Family, former Commandery Princess Zhaoning and Crown Princess, Grand Dowager Empress Shen Xihe.