Why was Paul called Mercurius in the pagan city?

Les explains that Paul and Barnabas were in a pagan city, and the people called Saul, or Paul, Mercurius because he was the chief speaker, the preeminent speaker. Les points out that the word chief comes from the same Greek word used elsewhere for the chief man of the island, the governor, the chief priest, and the high priest. He asks whether that indicates something bad and answers no; it denotes a place of leadership, the head of the line. That same idea of being the head of the line is then tied to Paul’s words that Christ Jesus came to save sinners, of whom he is the head of the line, and that he obtained mercy first as a pattern.