[goatlover]

By the time Paul was writing a few years after the crucifixion, the Jesus movement already believed God raised him from the dead, which made him the exalted messiah in their minds. So it's not too far a stretch to think they believed he also performed miracles while alive. In the Hebrew scriptures/OT, Jewish prophets performed miracles. Why not Jesus?

In the canonical gospel accounts, God's spirit enters Jesus when John baptizes him. Then he starts his ministry which includes miracle working. The disciples did the same thing in Acts after receiving the spirit. There is an even a false prophet (from the Christian POV), Simon Magus, who could perform some miracles.

There was widespread belief in miracle working in the ancient world. It meant the miracle worker had been empowered by the gods, or was a son of a god (or Yahweh in the case of Jesus).