suppose every THING can't be THE most important thing. However, multiple things can be essential. And various things can be the most important in their own arena. So far in the letter to Corinth we've witnessed the emphasis of several different things, most notably - love. Certainly, our Christian walk should be permeated with God's love, but what is the proof that our love for God & for our fellow man is indeed the one thing that God uses so effectively? Well, while love is the supernatural effect of the gospel, the truth of resurrection is proof of the validity of the same gospel. The resurrection proves God’s love claim.
The gospel is certainly presented flawlessly, clearly, and simply here. And, the fact that Jesus rose again is an essential part of the gospel. Without it, the gospel becomes a petty mockery and an irrelevant nightmare. So, let it be said again that Peter saw Jesus alive after His crucifixion, as did the rest of the apostles (1st Corinthians 15:5. And, Jesus was seen by over 500 believers who were willing to testify about it (vs. 6); and by Paul, on the road to Damascus (vs. 8). Jesus is alive. If He wasn’t, all would be lost.