Paul knew stuff!
In the previous verse, Paul reminded the Corinthians that when he first came to their town, he did not present the gospel to them with lofty speech or human wisdom. In other words, he did not call attention to himself by performing feats of verbal gymnastics as some entertainers of their day did. He did not wow them with a display of his great personal wisdom. Orators of that era were much like entertainers—and Paul did not want to confuse the compelling truth of the gospel with mere entertainment.
Now Paul adds that he made a conscious choice not to display his knowledge about anything at all except for Jesus Christ and His crucifixion. It is not that Paul did not know about anything else, of course. He was well educated and experienced;
“...though I myself have reason for confidence in the flesh also. If anyone else thinks he has reason for confidence in the flesh, I have more: circumcised on the eighth day, of the people of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; as to the law, a Pharisee…” Philippians 3:4–5. “Now when they had passed through Amphipolis and Apollonia, they came to Thessalonica, where there was a synagogue of the Jews. And Paul went in, as was his custom, and on three Sabbath days he reasoned with them from the Scriptures, explaining and proving that it was necessary for the Christ to suffer and to rise from the dead, and saying, “This Jesus, whom I proclaim to you, is the Christ.” And some of them were persuaded and joined Paul and Silas, as did a great many of the devout Greeks and not a few of the leading women.” Acts 17:1–4. “I am a Jew, born in Tarsus of Cilicia, but brought up in this city. I studied under Gamaliel and was thoroughly trained in the law of our ancestors. I was just as zealous for God as any of you are today.” Acts 22:3.
At least for these particular people, Paul wanted to be sure they weren't attracted by spectacle or entertainment. His mission was not to impress them with all he knew and could talk about. Paul decided to focus on a simple, culturally radical mission: to deliver Christ's message to them.
~ BibleRef