Land doesn't vote, but groups do. The Constitution was written to accommodate both points, the Senate so each state has an equal vote, which is fair in respect to the fact that the Constitution is and agreement between states, and Congress where states with more people get more votes, because that is a legitimate perspective as well. It's not perfect to start with, and it's been modified poorly over time (representation hasn't been kept proportional in Congress), but it is fair to say that each state having an equal vote is one valid point of view, and the founders realized that it wasn't the only valid point of view.
Don't attribute the 'states rights' phrase to me as though I'm on the wrong side of the civil war or something. The country can't be entirely directed by states regardless of population, but the states can't be directed by other states based solely on population either.