The nogitsune chose Stiles because of his connection to all the supernatural beings in Beacon Hills and the Nemiton. And also because of the whole sacrifice thing left his mind open and made it easy to access his mind and possess him. Also he is brilliant and he is trusted. Stiles was perfect for the nogitsune. The fox had all the power it needed all he needed to win was a body with connections and a brain. Teen Wolf Season 3B.