Why did the fall of the Eastern Roman Empire not have the same impact on the world as the fall of the Western Empire? The world hardly cared about them and no one rushed to help them with their war with the Turks when they asked for help! What's so different about the Western empire that makes her more important?
You may find more context about the precarious geopolitical situation the Byzantines found themselves in by 1453 and the reasons behind the West's slow response to the siege in this post by u/enygma9753.