Kings fall into one of three categories, uttama, madhyama and adhama, said Kidambi Narayanan in a discourse. An ideal king consults his ministers and the elders in his court and uses their inputs too when he makes a decision. The one in the madhyama (mediocre) category, consults his ministers, but does not follow their advice. The one in the adhama (inferior) category does not consult anyone, but makes decisions himself.
Ravana carried away Sita, a sinful, unforgivable act of wickedness. He did not bother about the consequences. Even after the war began, he did not repent and return Sita to Rama. Had he done that, further bloodshed could have been avoided. As most of his warriors died in battle, Ravana felt that only Kumbhakarna could defeat Rama. So he woke up Kumbhakarna. Kumbhakarna told Ravana the process by which a king must make decisions. He said that a king should know whom to trust. Among the men who offered advice, there might be those who spoke sweet words, but their advice might be harmful to the king. There would be others who were not well read in the dharma sastras, and so their advice would not have the merit of justice. Some ministers might be in the pay of enemy kings. They might deliberately mislead a king. A king must protect himself by listening to the right persons. Kumbhakarna concluded that Vibhsishana had offered proper advice to Ravana. He thereby indicated that Ravana had rejected sound advice, and had acted against his own interests. Yet, because Ravana wanted him to fight Rama, Kumbhakarna did so, and was killed.
Ravana had the advantage of being advised by both his brothers. But he ignored their advice, refused to part with Sita, and eventually got killed by Rama.