Constantinople = Istanbul. How did the name changed?

When Mustafa Kamal Ataturk took over Constantinople he change its name to Turkey and the name of its capital to Istanbul. Why? It is simply because of this hadith

"Verily you shall conquer Constantinople. What a wonderful leader will her leader be, and what a wonderful army will that army be!"

No.1 - So that Muslims believe that this prophecy has been fulfilled.
No.2 - So that not many Muslims know where exactly is Constantinople, and couldn't relate the hadith above with any kind of situation.
No.3 - To confuse the Muslims - How could Muslim take over Turkey when its already rule by a 'Muslim' nation?

The mission of current Turkey government is to make the Muslim believe that this had happened when Mustafa Kamal took over Constantinople from Ottoman Empire which is the last Islamic Country practicing the Caliphate system.

The turning point is here - There's another hadith saying that Dajjal will appear 6 months after Muslims conquered Constantinople. But has Dajjal comes out after that incident? The answer is no. Which means the hadith above has yet to be fulfilled and it will soon Insya Allah when the real Muslim taking over Constantinople from the current 'Muslim' government of Turkey and restored Caliphate system. The name of Turkey has never been used by our beloved Prophet Muhammad SAW. It always been known as Constantinople and we Muslim must keep it that way.