What was the main reason for the emergence of the Radical Republicans following the Civil War?

Radicals led efforts after the war to establish civil rights for former slaves and fully implement emancipation. After weaker measures in 1866 resulted in violence against former slaves in the rebel states, Radicals pushed the Fourteenth Amendment and statutory protections through Congress.

I don't know if i'm right sorry if it's wrong

it was created as a proprietorship, unlike any other colony.

explanation:

did it already

it was certainly a debatable decision, mainly because it was based primarily on political - and not on legal or social - views. since the congress at that time was led by members of the republican party, and the territory that the tribes wanted to turn into an exclusively indian state was predominantly democratic, the proposal (as expressed in the constitution) did not succeed, but the constitution itself proved to be of crucial importance in the creation of the state of oklahoma, and, most importantly, it guaranteed the involvement of representatives of the indian tribes in the government of the future joint state.  

as a member of congress, i would have voted to ratify the constitution, or at least to have it tabled. ignoring it was an interested and partial decision.