Paul was a capable minister of the gospel of Christ because as Saul he was extraordinarily knowledgeable and upon his identity shift, Paul’s vast knowledge also shifted. His educationally attained knowledge became an encounter-based deep understanding of God and the scriptures. Paul was capable because he met Jesus, and Jesus equips those he meets.
Paul, despite popular belief, was not effective because of the considerable opposition he faced in life. The opposition came forth from his understanding and inability to back down from refuting false and incomplete teachings. The opposition he faced, strengthened his testimony due to his resilience, yes, but it wasn't the catalyst in his life; that happened on the road to Damascus and every day as he sought after God.
Paul teaches us, by example, that possessing just a head knowledge of a thing cannot combat a true and deep understanding of a thing, especially on spiritual matters. Understanding trumps knowledge every day.
Do you have head knowledge of God? Let today be your Damascus Road day when you let God change that knowledge into understanding.