There’s this thought experiment in game theory called the Prisoner’s Dilemma. Wikipedia has a good write-up here. There’s a lot of argument about what a wise person would do, not knowing what the other person will do, and I often consider it while playing Diplomacy.
Game Theory doesn’t seem to address the fact that you can only betray your partner once. Then they will always betray you, and that’s the worst outcome. Often it is worth it to take a risk now so you don’t guarantee failure later.
That’s why I like playing series Diplomacy and not just one-offs. There’s a world of difference between a single game and a seven game series with the same people. They’ll remember a betrayal or a compromise. A lot of people in politics are blind to the notion that they’ll have to deal with these people in a few years and a few dacades.