Its fundamental, you don't need to be a genious to see it.. for example. If Senators were elected by state legislatures and sent to represent the states, and could be recalled by their governor at any time that you would have the insane party line chaos that happens in Washington? Where individual senators will vote a party line regardless of what it does for their state, like for instance the Clinton Tax Increase in the 90s, where party loyalty was more important than anything.
Its crazy to believe that the people and the state will have exactly the same desires. A state is going to be interested in the matters of the state and government, while the individual will be interested in self interested issues. If you think the state and the people will share completely the same interests, then there is no reason to even have states.