What I learned from the whole Marlo plotline was that neorealism, which is a theory of international relations, is so good that it even applies to everyday life as an individual.
Stringer Bell and Joe and all the other guys who were so heavily invested in cooperating followed liberal institutionalism, which is a competing theory in IR.
Both neorealism and liberal institutionalism agree on one thing, which is that the world of nations is an anarchy. There is no effective law enforcement system for world politics. If one country has a problem with another country, it can't be solved by negotiations, and it also can't be solved by taking it to a court. So it's called an anarchy in that there is no effective mechanism for solving disputes, other than military force.
Liberal institutionalists believe that if we can set up strong enough institutions, then we can work together to bring about world peace. Woodrow Wilson was one of the big believers in it. It's why he was the main force behind the creation of the League of Nations, the predecessor to the United Nations. So they believe that if we can set up a co-op between all the nations in the world, any problems that might arise can be solved by the group. "If anybody has beef, we don't have to take it to the streets, we can bring it to the group," like Stringer says when he's trying to sell the Co-Op to the others.
Neorealists believe that institutions aren't worth much, and that the only way world peace can ever be achieved is if one true superpower emerges and conquers the whole world, to such a point that nobody dares resist or fight against them. That superpower world conqueror would then be the world's police force and law court. Anybody has a dispute, you bring it to them, they settle it personally. This is basically the system that Marlo sets up in his "price of the brick going up" speech.
The problem with liberal institutionalism is that it only takes one person who doesn't want to be part of the group and who doesn't care about the group, like Hitler in the 1930s. Someone who's got his own agenda, and isn't interested in cooperating. And the whole system falls apart when that happens, just like the League of Nations did. Even if you're part of the group you have to make sure that as a collective you're strong enough to force someone who doesn't want to play ball out of the game. Or at least, force them into your group.
That's what Stringer and especially Joe overlooked. They all should have backed Avon when he went to war with Marlo. If they all worked together they would have smashed him, and then their co-op would roll on until the next time someone else tried to challenge it. But instead they just decided to sit it out. With Avon out of the picture then there was nobody left strong enough to fight Marlo, and it was inevitable that he would come to dominate them all.
