Restoring a man and driving a herd of pigs (which no observant Jew should have kept) was too much for some. The people responded with fear rather than faith:
Luke 8:37 And all the people in the region of the Gerasenes begged Jesus to go away and leave them alone, for a great wave of fear swept over them. So Jesus returned to the boat and left, crossing back to the other side of the lake.
The man He restored stayed behind and told everyone the great thing Jesus had done for him.