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."

concurrent jurisdiction is the ability to exercise judicial review by different courts at the same time, within the same territory, and over the same subject matter. for instance, a domestic violence matter may be heard in either a general civil court or a family court in the same county. whichever court actually exercises its jurisdiction first will do so exclusively.