They were critical of Jesus and Nicodemus dares to speak up. Now, we see Nicodemus publically standing with the Savior. We see him helping with the burial of His Lord and friend. How proud the Father must have been of His disciple. We see him go from a questioning skeptic to a faithful follower.
Spiritual maturity takes time.
He had been raised in a Unitarian church, in almost total ignorance of the gospel, but when he had moved to Boston to make his fortune, he began to attend a Bible-preaching church. Then, in April of 1855, his Sunday school teacher had come into the store where he was working and simply and persuasively shared the gospel and urged the young man to trust in the Lord Jesus. He had, and now he was applying to join the church. One fact quickly became obvious. This young man was almost totally ignorant of biblical truth.