I did not really like how fast and loose with history you were, so I will just say that they did not clean up their act on their own, but were forced to. Many things have been forced on the states judicially, brown v board of education, baker v Carr/wesberry v sanders/reynolds v sims all forced more equitable voting schemes(ie, handling gerrymandering) etc are some easy examples I could think of for how your idea that the states figured themselves out is a misconception.