The defeated countries lost many territories in the aftermath of the great war, but I do not know why the allies (possibly just the British?) did not cede Constantinople/Istanbul to Greece? They gave them a large amount of territory relative to their nation's size but not one of their ancient capitals? Poland was created, Romania, Yugoslavia, Lithuania but no Byzantium/Eastern Rome?
Maybe the Eastern Roman Empire/Byzantines were irrelevant and long dead in the eyes of the west and left it to Turkey? I don't know. It's not a simple question to google