But don't forget that the Gospel that Paul preached came from the Resurrected and Ascended Jesus Christ. He received it directly and personally on the road to Damascus and he spent many years with the Lord before he began his ministry.
And you need to not forget that before he had his conversion on the road to Damascus,(he didn't receive the Gospel there) he was on that road to jail and have killed more Christian converts! Don't forget the Apostles were originally very wary of him because of his previous reputation and habits.
They had already been converting Christians to the Church which he was imprisioning.