Let’s go through the story. It’s the Sabbath, so like a good Jew Jesus is off to synagogue.(1:21) We are told he teaches them as one with authority, and not as the scribes.(1:22. Remember, this is Jesus on the scribes ’ turf.)And then a demon-possessed man confronts him.(1:23) Defiance on the part of the demon soon becomes fear.(1:24) Jesus then exorcises the man (1:25-26) and once again those in the synagogue marvel at his authority to teach and heal. (1;27. Note that there is an alternative translation at this point ; “A new teaching! With authority he commands even the unclean spirits, and they obey him.”)
Notice in this story that the content of the teaching of Jesus is omitted. Notice also how the specifics of the exorcism are hardly mentioned, unlike other stories of healing and exorcisms we get in the Gospels. (For example, Mk 9: 14-29) Notice also that we are told not merely that Jesus taught with authority, but that his authoritative teaching was unlike the teaching of the scribes. And the story finishes with another discussion of the authority of Jesus, making the story of the exorcism framed by discussion of Jesus’ authority, before and after.
That’s why this story is not exactly about the content of teaching of Jesus. Nor is it merely a story demonstrating Jesus’ power over the demon, otherwise why frame the exorcism with the contrast between Jesus and the scribes?