Upon touching the wall at the conclusion of the final of the 100-meter freestyle at last summer’s Olympic Games in Paris, Pan Zhanle turned toward the scoreboard inside La Defense Arena.

Chinese swimmer Pan Zhanle said foreign athletes at the Paris Olympics “acted like they didn’t care about medals” but had a “breakdown” when they saw Chinese rivals atop the podium.

Pan Zhanle did the unthinkable on Wednesday in the men’s 100 meter freestyle. The 19-year-old didn’t just break the most ...