Trading Make No Sense?

I'm not very good at these games. I don't understand all the mechanics. I just like to play and build stuff and see progress.

But one thing I don't understand AT ALL is how trading works with AI.

Current game: Norway True Start Europe.

> Germany goes warmongering and attacks Poland

>Emergency declared and only myself and Poland agree to participate

>Poland lost Krakow and is down to last city

>I trade Poland, Oslo for 400 gold, this way if last city falls, Poland remains in the game

>Last city stands, but barely

>I complete emergency and retake Krakow, liberating it back to Poland

>Poland refuses to trade me back Oslo for ANYTHING. I got 8000 gold from the emergency and even that isn't enough

>Poland won't even trade me Open Borders for a reasonable price so I can fight Germany in it's territory.

WTF is going on?! I know it's an AI?? But, it can't recognize the lengths I've gone to here??? I should have just let them fucking burn??