Autarchial Succession - How Does It Look From Outside?

The brain-eating thing seems to be a secret, and as Vodalus says, they may reign a half century or a fortnight. But what story is told to the Commonwealth? What keeps people seeking to corrupt the process in their favor from discovering the secret? What gives the fealty-swearing vasals confidence that the new Autarch isn't just someone who planted a bug on the old Autarch to learn the mastering words and then did him in?