Ai and happyness

So i'm still playing a marathon game on the largest map and something I am beggining to notice as I come into the end game is that the ai has a crazy bonus to its happyness that allows them to expand crazily early, but that they seem to expand even past this with no regard for thier unrest. Im currently fighting a giant german empire that has almost limitless armies, but each one drops like paper with -24 strength

Yes, AI is flavor driven and gets bonuses. Late game indicates Bismark is likely suffering from ideological unhappiness (from low culture flavor) while stubbornly holding on to whatever it is.

Along with bad ideology, over expansion can also cause unahppiness since each city = 4 unhappiness in a civilization or empire.