The first dictator of North Korea was Kim Il-Sung. The split was when the Japanese empire was dismantled at the end of WWII. Korea became part of the Cold War. It was divided into two "spheres". With America's influence in the south and Russia's communist regime in the north.
The new Americans found there to be too few limitations on the power of the federal government the bill of rights states that we all have individual rights as well as sets limits on what the federal government can do. Hope this helps!