Two children share one cake and one child's gain is the other's loss. Two neighbours swap mangoes for apples and both end up better off, with no new fruit. Telling these apart changes what you should do.
Betraying your partner is the correct choice no matter what they do. So both of you betray, and both of you serve five years instead of one. No error was made — and that is exactly the problem.
Two petrol stations cut prices until neither can move without losing. Nobody wanted the result, everyone behaved sensibly, and it held anyway — because stable and good are different properties.
A rising power wants influence matching its strength; an established one sees each concession as erosion. Both are sincere, neither needs to want conflict, and the pressure builds anyway.
Most commentary is about which leader decided what. Constraints — geography, resources, neighbours, demographics — explain the menu of realistic options, and they outlast every government.