i am generally the aggressor in my games, but i accept that the ai is somewhat lacking in the intelligence dept. especially when it comes to diplomacy. i don't believe there is much ryme or reason to it either, simply look to the papacy and the sillyness there. i can be allied with many factions, but none will help you out in a pickle, is there even the option to call upon them for help?, leaves something to be desired, imo.