If you want a simplification the powerful slave owners who were a minority mostly cared for their bottom line which necessitated slavery remaining legal which meant states had to be able to declare their own laws outside if those solely invested in federal government by the constitution the same but opposite for the factory owners of the north. Everyone else had a myriad of interests including just basic freedom from a segment of the country that to this day views them as undignified hicks deserving to be mocked.