I was trying to defend myself with culture. I noticed his culture creeping towards me so I upped the ante. I buildt all the culture buildings that I could and cranked the culture slider to 50%. I also buildt Hermitage in my one and only city. It seemed like a waste. It turned out to me not enough.
I really should have been playing OCC, but I arrogantly thought that I might get five cities or so when I planned the game and started running Map Finder. As every milestone came and went with failure (missed the Oracle by 3 turns, missed Liberalism by 2 turns, etc.) I should have abandoned the game. As the culture creaped towards my capital, I just thought "A few more tunrs and I will get my PA to win the game." It turns out that my soon to be PA just wanted to take me over via culture.