Throughout the book of John, Jesus performed miracles, signs and wonders. But true faith in Christ isn’t based on if God does something cool. True faith in Christ is based on the person of Jesus Christ and who He is, not just what He does. Therefore, everything He did was so you may believe that Jesus Christ is the Son of God, the Messiah our Savior.
Now Jesus did many other signs in the presence of the disciples, which are not written in this book; but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name. – John 20:30-31