Since when was Anora a bad ruler? Or Cailan, for the most part?
There are different types of "bad" for the record. None of those leaders possessed all of the qualities a leader must have for it's nation to flourish. Sure you can make do, but ultimately alone they were all flawed in some way as rulers.
Anora was way to harsh and unforgiving. She will not earn the loyalty or respect of her people alone.
Cailan was a moron, and while he would be loved. He would make political blunder after blunder.
Logaihn was so racist and traditionalist that he would see his country die before he seen change.
These particular qualities are all extra crippling for a leader to not posses. I kind of liked how the Dev's showed this.
Anora and Cailan were probably the most effective working together. All it would take though is just one of them dieing and the system falls apart.
Like I said they all lacked a fundamental quality necessary for a truly inspiring and good leader. Sure you can call it human, but I call shenanigans.