Symbolika1:
For me it's because CX never told her frankly and simply her true man's feelings. And also XiaoYao would have had aknowledge that they are not real Cousins/Gege power => much earlier.
Because when she meet her man's trio firstly when she was still a man - it was a close timing for them/all to get equitable a chance than. And it would have been a perfect timing for her too to learn her true parenting line at that moment somehow...To even take time to , while still in a man body, probe them all...
He would than have equitable chances to win her heart:):
TBH, if CX confessed to XY right at the start, we wouldn't even have a story, since the other 2 guys would not have a chance. CX has always been number 1 in XY's heart, even at the end of the novel after she's with Jing.
I would call this pairing beautifully ill-fated, as YZ even said that CX had a chance at the very start, but circumstances make it that them being endgame would never have been a possibility, except in an alternative universe where their family members survived.