Okay so here is my take
It's JiHeng fault yes, her selfishness triggered a domino effect which along with destiny's supposed test to their love cause him to take 73 days to stabilize the chasm.
He is Dijun, and saving the world will always take precedence.
For the matter of ZL explaining to FJ, He didnt know till DJ returned in the book. But there are other factor's that cause FJ to go to the mortal world
Book version: She knows he wont just abandon her so she waited till she could and then three major things happened
1. she found out she was pregnant
2. that Dijun altered her memories in Aranya's dream
3. Her entire family convinced her that he abandoned her which she chose to believe due to reason number two.
In drama version:
same except no point number two.
FJ has always always had lack of confidence in DJ's love for her because she simply cannot forget the humiliation she endured for him when she was a maid. IT was BAD. and she never really got the time to get over it
Second, her family were NOT happy that she was marrying Dijun. Especially her father. So they chose to believe the worst without proper investigation and shut down all means to communicate with the heaven clan and also practically forbade Dijun to ever meet her when he came back. For them, because Bai Yi was possessive of FJ and was unhappy she went through so much hurt because of Dijun( which will naturally upset any father) he CHOSE to be blind and believe the rumors instead of investigating
This is the part that really annoys me off still now, the Bai family are powerful and well respected
Yes you endured humiliation, but when the man tried to explain, you shut him out??
You dont go and investigate? I mean Bai Qian is the crown princess for gods sake. Mind you Bai Qian and Zhe Yan were still receiving letters from FJ, so if they wanted to they could have helped resolve this issue eons ago. But they too were blind but the hurt and decided to not care.
This is maintained in both drama and book: Bai Qian of drama says, though she is married to the heaven clan, she will always put QingQu first.
So after repeated rejections all Dijun could do is prepare to battle Milaou and try to see FJ one last time before he dies.
In the book, FJ actually a solid reason to leave; her insecurities plus dijun altered her memory which god was such a wrong move
But the drama made it look as if she chose to abandon him and ZL later gets into her face and basically calls her out on this .
So yeah, if you think about it, it's not just Dijun or FJ or fate; it was a lot of people and their choices. A lesson here I felt was: if we keep using the past as a reason to supposedly protect ourselves in the present, there is no guarantee that the future will be safe; it might be worse