From the historical perspective of great dynasties of civilized societies, central government is basically a byproduct of power struggle. One powerful group wants to impose their power on everyone else, or perhaps the whole society wants to impose the collective will on everyone else, so they create a central government. When that doesn't happen, you get nations which are tied together by common bonds, but they decide matters by convening councils and mutual agreement and compromise, and don't attempt to force their will. But all are usually happy to force their will on other nations.<p>Generally speaking, cultures that have strict observances of Gods that require things of their peoples are a lot more into imposing their will on others. Every society collectively agrees to buy into the way that society works, because the implicit threat is that if you don't buy into it, your neighbor will kill you.