If the AI surrendered a little bit earlier than it does, while it still had some assets, and mmmmaybe didn't surrender to its best friend all the time, but to someone who was the more powerful of the remaining AIs. It could factor in:
.3 How much they like the other civ
.6 how powerful they were (the more powerful the better)
.1 how much the other AI likes me. If it liked me... they would favor it less.
If the AI surrendered in this way earlier it would be more challenging to deal with the remains of whatever they had integrated into more challenging opponents. Not some wimp.
Just my thought.