How did the kansas-nebraska act contradict the missouri compromise?

idk but found this on google

"the kansas-nebraska act allowed each territory to decide the issue of slavery on the basis of popular sovereignty. kansas with slavery would violate the missouri compromise, which had kept the union from falling apart for the last thirty-four years. the missouri compromise had prevented this from happening since 1820."

answer; eliminate parking problems in cities, because a car took up only half as much space as a horse and buggy;