Demonmir became a renegade.
He chose to do it because he saw profit in becoming one.
Ottoman was done being the lapdog for any establishment part of the Anfang Alliance. It seemed that he preferred to take his chances with half-bloods labeled as all-season targets by the Anfang Alliance than limit his potential as a demonic ranker.
Demonmir knew he could progress faster if he became half-blood. Plus, the Demon Prince consciousness inside him didn't like serving establishments as well. With the Last-Blood Bastion, he would have much more freedom.
Demonmir's involvement with the half-bloods complicated Eren's life. He wasn't sure whether to stay in business with them or pull out. He didn't want to nurture his own enemy after all.
