“All the people agreed to grant Simon the right to act in accord with these decisions. So Simon accepted. He agreed to be the high priest. He agreed to be the commander. He was the ethnarch of the Jews and priests. He was to be protector of them all.”
There was a kind of social contract. Simon agreed to act in accord with their decisions which gave him all this power. He accepted being the high priest, the commander of the army, and the ethnarch of the Jews. Ethnarch was the Greek title of leader of an ethnic group, something like a general or governor, but less than a king. Interesting enough, it is a Greek term for someone who had been fighting the Greek influences on Jewish life. In the 1st century CE Herod will be called an ethnarch. Someone had to accept this authority. He agreed that he would protect the Israelites with all his power.