Towns and cities in the ancient world were not as big as they are today. When visitors from abroad come to visit a town, news of their arrival would spread, especially if they sought to speak in the public square and share a new/controversial message. People were generally eager to hear what such visitors might say, and invited their friends to join them in the audience.
4 La population de la ville se divisa: les uns étaient pour les Juifs, les autres pour les apôtres.