I'd have liked to see more actual reasons for the departure beyond "not a good fit anymore". What does that mean? How have things changed? Honest question, I'm

I'd have liked to see more actual reasons for the departure beyond "not a good fit anymore". What does that mean? How have things changed? Honest question, I'm not after dirty laundry. Just want to know more than "I'm leaving because reasons" which is kinda the tl;dr of that post.