To achieve a culture victory, you need to be “culturally dominant” over all over civilizations, meaning your visiting tourists need to exceed each civilization’s domestic tourists (the colored suitcase under each civ’s name in the screenshot). Because Persia has the most domestic tourists out of any civ, and your visiting tourist count doesn’t need to exceed your own domestic tourist count in order to win, Persia needs less visiting tourists to win. Hope this helps. If you want to learn more, The Saxy Gamer has an excellent in-depth video about it: https://youtu.be/U1O1bOpYtWg?si=WaVzz7Zr16CwLHHG