The naturally minded people who thought Jesus was being literal left after He said they had to eat Him. The spiritual minded understood it to be a spiritual teaching and didn’t accept physical cannibalism as a form of worship.Rationalising Jesus words is not the same as believing Jesus words. Rationalising is the opposite of believing, the opposite of Faith.
Faith is the key, Faith goes beyond human reasoning.
Jesus flesh is real food and His blood is real drink.
Believe it because Jesus said it.
“But a natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually discerned. “
The Catholic Church made it doctrine at the Fourth Council of the Lateran in 1215. Of course they will say God was doing it all along. And it didn’t happen overnight. So yes there are going to be some people who taught it before the Catholic Church made it their doctrine.
It is merely an example of humanity who discerns naturally making a mistake about what Jesus was teaching.
Since Jesus said the words He spoke were spiritual words, He was telling his disciples that he did not mean they physically ate him. It meant that spiritually, they took Him into themselves.
To make it a physical thing is to teach the opposite of Christ.