TL;DR: Dana has been harboring some resentment over the way the Bucks were treated after Brawl Out. While The Elite themselves have decided to let bygones be bygones, she was never that happy with the situation.
Morffi, OTOH, simply had a better offer elsewhere.
Is she really that inexperienced? In terms of pro-wrestling merchandise pre AEW she was running probably the biggest game outside of WWE, and maybe NJPW.
I don’t think she had any previous work experience in that position. It was probably a we just need to get up and running situation. I’m honestly surprised she was still filling the role.