This must have been a family wedding since Jesus' mother was there. She traveled with them briefly afterward. Jesus command over the simplest thing here impressed everyone.
This chapter is an introduction to the the development of the faith of the disciples. They believed after the miracle. They remembered the Scripture as he was cleansing the temple. They believed the Scripture and Jesus' words about raising the temple. . . after Jesus arose. John seems to want us to see what caused them to believe in Jesus.
Jesus did not entrust himself to them. Literally, "he did not believe himself to them," even though they believed. There is a belief that is inadequate for knowing Jesus. Yikes.