John 2 ends on this note: Now when he was in Jerusalem at the Passover Feast, many believed in his name when they saw the signs that he was doing. But Jesus on his part did not entrust himself to them, because he knew all people and needed no one to bear witness about man, for he himself knew what was in man (ESV).
I have always had a bit of a soft spot in my heart for Nicodemus. Jesus is the new kid on the block, the new radical. He is already stirring up problems for the religious establishment, and Nicodemus takes a pretty big risk. He comes at night, during his normal study time but also under the cloak of darkness, and wants to talk with Jesus face to face.