subj. it makes the game really dumb because in like 30 minutes i am left with only one opponent huge AI kingdom because all others have surrendered to it
How can i fix this? thx!

Thats really a dumb thing, which makes winning annoying.

you have to live with that and build your strategy "around" this. I dont know how often I felt like a winner, just to see my strongest opponent grow just of surrendering kingdoms, sad.