Why did Jesus leave Samaria? The people there believed in Him, accepted that He was the Messiah. He could have had a much more successful ministry amongst such accepting people, right? Then again, if Jesus had been accepted as the Messiah He couldn’t very well have fulfilled the plan God had for the Messiah, could He? John has already made clear in the prologue that Jesus came to His own and His own rejected Him. So, Jesus sets out for Galilee again, to those who will not see Him for who He is.
However, when He arrives in Cana the people greet Him with excitement. They had also been to Judea and had seen His miracles there. They were likely part of the crowds that “believed” in Jesus due to his miracles. Those that the John has already said were “believing” in the wrong way.
When the official arrives and asks for Jesus to come heal his son, Jesus confirms as much. It is with exasperation that he declares of the crowd that they need to see signs and wonders. They wanted Jesus as a supplier of needs and an earthly power. Jesus’ message is altogether different. He is declaring a need for repentance, a change, in light of the Kingdom of God. Jesus wants people to surrender and trust.
But this man seems uninterested in signs and wonders. He is only concerned for his son. When Jesus tells him his son is healed, the man doesn’t stick around to see Jesus’ power. He doesn’t try to convince Jesus to come with him, “just in case.” He simply heads back home, in the hope that his son is indeed better.
And once he confirms that Jesus’ word and power were true, he became a true believer. Interestingly, his first act as a follower was apparently to lead his whole household to believe in Jesus as well. So far, every conversion in the Gospel of John has led to a multiplication of followers through testimony.