Kintan was in the part of the Outer Rim where the Hutts were dominant. The Niktos there worshipped a nearby supernova which occasionally told them to revolt. At one point the Nikto were so completely beaten that they were ordered to serve as the Hutts' butlers for all future generations. This was how the legal system worked in those days. Since wars against the Hutts seemed like a bad idea, they engaged in a series of civil wars over the next 20,000 years. After that Kintan was accepted into the Republic.