These are just my opinions and ponderings. I've always thought that the Autobot leader during the golden age of cybertron was not a absolute ruler. He was chosen by the Matrix but he had a council of elders (like congress or parliament) to answer to also. I remember this being the case in the old g1 comic. I think during times of crisis the council voted the Autobot Prime emergency authority and when the most recent war became a blood (energon) bath those powers were never taken back. The Decepticon leader on the other hand is a absolute ruler that holds power by firepower, intelligence and brute strength. Not necessarily in that order though. That's why ole Screamer was about to have himself crowned because that's virtually what he would be, a king. But Galvatron disagreed with him quite violently I remember.