Two factors:
1) I was being very aggressive in setting up a Leon vs Paul situation. I threw my original plan to be subtle to the wind because I felt extremely confident in my allies' positions. I clearly did not read the room correctly!
2) I was drinking all day on 4th of July and got very hungover so was unable to respond to messages until 3pm Sunday, so I was out of the loop for a loooong time. Meaning I was unable to react to changes in diplomacy.
This combination led to my downfall. Oops.