I Corinthians 2:4 And my speech and my preaching was not with enticing words of man’s wisdom, but in demonstration of the Spirit and of power: 5 That your faith should not stand in the wisdom of men, but in the power of God.
Paul was careful to use God’s Word to see people saved. He was not trying to convince them with enticing words of man’s wisdom. This doesn’t meant that he couldn’t speak or wasn’t smart. It doesn’t mean that he didn’t study his Bible and prepare. It does mean that he used the Bible and not philosophy to convince men to be saved.
It wasn’t how good he could debate and argue. It wasn’t using the philosophy of man in his day to convince them. He simply presented God’s truth and expected God to make it ring true. It was God that would convince and convict. It was God that would bring them to repentance.
If you are a really smart person and know how to win debates you might get people to follow your logic, to be convinced by your rhetoric but will they be convinced by you and your abilities or Him and His power.
Paul didn’t try to put the Bible in the best light and convince men that it was reasonable. He just told the truth about Jesus and His crucifixion and let God do the work.