Constantinople became the center of the byzantine empire because

Because Constantinople knew how to take advantage of its privileged geographical situation, which made the city an obligatory passage for caravans that brought East and West into contact. Therefore, trade was undoubtedly the great basis of the Byzantine economy.

Until 330 it was called Byzantium, and then, until 1453, Constantinople. Its current name, İstanbul, was given on 28 March 1930. Istanbul was the capital of the Eastern Roman Empire and the Ottoman Empire.