Being intelligent isn't enough, especially if they have their self-interest in mind rather than the will of their constituents.

Are you sure? I mean have you been watching the impeachment proceedings? Intelligence doesn't seem a virtue of congress at the moment or Trump would have senators from BOTH parties with pitch forks outside his door.

Sure, but they are similarly self-interested, if not more so.

Yet they manage to invent and vote for absolutely atrocious laws. I bet their intelligence is highly concentrated on improving their own agenda whatever that be rather than well being of general populace.