The wars in the world won't stop unless the powerful state won't stop thinking to exercise their authority on the weak countries. They build the weapons to test on the weak countries - like we have witness so many examples in the history where the weak suffered and powerful ruled.
You have a point. From what I've observed, the big and developed countries tend to bully those who are small and weak. I don't know if what they get from it exactly. If is it feeling satisfied or just for the sake of letting them be a guinea pig for their weapons and aspirations. Mostly, they also take advantage of the situation because little countries cannot do anything grand or complain for what they are doing.
You see, some countries fell into cowardice just to avoid war. They tend to settle and meet halfway for the sake of their nation and their citizens. Despite all the organizations, when a country wants to bully one, majority can't do anything because the tension will just grow bigger. The best example would be Russia-Ukraine war.