The BIA and the feds were in bed with the corrupt tribal leaders for decades and looked the other way and often even supported them. Basically, it would take the feds preventing intimidation and corruption leading up to elections - when tribal leaders control your allotment of benefits and their authoritarianism prevents job creation on the rez, you're screwed.
That’s exactly right. But again, its up to the Indians themselves to rid the tribal governments of corruption. Uncle Sam can’t do it, and any attempt to do so would be met by a solid wall of Indian resistance based on principle.