There is a major difference between knowing a method and having a personal relationship with the Person whose name carries with it the power to accomplish a miracle. Paul knew the Person! They only wanted the fame from doing a miracle with a method.
This stark difference is witnessed by those in Ephesus watching these things take place. “And fear fell upon them all, and the name of the Lord Jesus was extolled” (19:17b). Notice carefully: Paul was not exalted by the people, but the Lord Jesus, even though God used Paul as His instrument. This must be the governing principle in every ministry – that the name of Jesus in lifted up, not the servant or instrument!