Answer:
The people of the area had pre-existing Socialist ideas.
Step-by-step explanation:
The Socialist Party of Oklahoma was centered in the former Indian Territory because its leaders considered that its socialist ideas, which included (and still include today) concepts such as collective ownership of land, centralized planning of the economy, equality absolute between individuals, etc., were similar to the concepts of property that were established in the laws of the Native Americans. In this way, by establishing their centers in the native territories, the leaders of the Oklahoma Socialist Party believed that there they would have high rates of support, which would allow them little by little to grow in national politics.