You're assuming the gospels are historical records, whereas they're works of theological propaganda. The writers put in Jesus's mouth words that would be relevant to later audiences, such as to those who would start to doubt or to fall away, to make Jesus seem prophetic.

In any case, Dostoevsky's parable of the grand inquisitor nicely explains why the church had to lose its focus on Jesus, by replacing the man with "Christ," with the theological character that was a figurehead and a puppet of the church.