I think there should be a way to gain popularity. Once you are at war with anyone (which this is a war game by the way), the popularity keeps dropping. And once you are at war with one AI, it drops faster, and more and more AI declare war.
I had allies with shared map, who gone inactive on me, and eventually because of AI and a dropping popularity, I am now at war with several of my allies.
It is impossible to gain a truce, ceasefire, peace or anything else with AI, something which is completely absurd, so even if I wanted to make peace with some, I can't. And why a previously unprovoked ally turns into an enemy is beyond me, just because AI took over.
Currently I have 11 AI at war, with popularity of 13, but I manage to maintain morale between 65 and 75 by just slowly taking some of the land from the AI closest to me and then wait a day, while taking out the smaller AI enemies as quickly as possible.
Of the 25 players, only 3 active players are left, including me. and I am the largest country, so obviously most do not like me.
It is possible for me to win this map, slowly by attrition, by attacking only a few provinces in a day and use my army to stomp out any rebels. Building forts along the very long Russian border, while I take care of the smaller countries 2 at time, and offering peace/ceasefire to the rest of the 9 countries at war.
The AI is stupid. They declare war, but don't actively attack, most of it, is just a ploy to lower morale.
And the few which do attack, they spam me with anti aircraft. Occasionally with a small tank. So I can easily swat them like flies.