Write about pluses political regime "oligarchy"

You mean what possible advantage could Oligarchy have?

Oligarchy could mean that people in power will have good education and for example won't be manipulated by populists. For example often people choose their representatives based on very little information, and in an oligarchy, where a small portion of a society (the riches and best educated) rules, it could be more likely that the rulers will have the necessary education and preparaation.