Mark's gospel presents Jesus first & foremost as a spirit-filled exorcist from a baptism by John in which the spirit comes into him. It is in the spirit world that Jesus is first recognized. In fact, Jesus is confronted by "unclean spirits" in individuals everywhere: in Galilean synagogues (Mark 1; esp.1:39); on the margins of life (Mark 5, the Gerasene demoniac) and beyond Galilee (Mark 7, the Syrophonecian woman on behalf of her daughter).
And it is not just individuals: people are enthralled: ".. they kept asking one another, “What is this new teaching? With authority he commands even the unclean spirits, and they obey him!” Crowds from everywhere find Jesus; to avoid being crushed he gets into a boat offshore. But "whenever the unclean spirits saw him, they fell down before him and shouted, “You are the Son of God!” (Mark 3).
Not surprisingly, critics accuse him of being demon-possessed: "but how can Satan cast out Satan?" Jesus responds. Rather, Jesus' self understand expands: when people pursue Jesus to the extent that they "unroof the roof" of the house where he is to obtain healing for a paralyzed friend, Jesus demonstrates an ability to forgive sins on earth as Child(son) of Humanity (2:10) right before the healing takes place.
Even his own household (family) members, when they hear these events, believe that he "is beside himself" or out of his mind.
Josephus connects spirit possession with social and political stress, as is likely to be the case in Galilee, where Mark locates Jesus' ministry during the time of Herod Antipas. (Teaching a new course on Jesus has given me a chance to re-think Mark's Christological emphases).