When he said it was by hearing and believing that man would be saved, you mean he did not know man could not hear and believe?
Wait a minute he must have forgotten all the old testament saints, that left this earth in faith, and are in heaven today. that did not have the Holy Spirit to draw them.
He must have forgotten they had faith in his word, and mixed faith with what they had heard the gospel.
Do you suppose he did not remember he said man was born again by the word of God, and some would say by regeneration and then they believed.
I personally believe he knew what he said and he also knew, as did the father, that he Jesus paid the ransom for all of mankind, and those that believed on would receive him.
Joh 1:12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name:
Mr 16:20 And they went forth, and preached every where, the Lord working with them, and confirming the word with signs following. Amen.