Why are the majority of Shia in the world located in Iraq, Iran, and surrounding areas? Why not in Madinah?

And why are the Sunnis all over the world? I am just trying to understand why this phenomenon is present, considering that Rasulullah (saw) and Ali (ra) were located in Madinah, and the first and the best Muslims were in Makkah and Madinah. How did it become so that the true Muslims shifted to Iraq and Iran and... show more And why are the Sunnis all over the world?

I am just trying to understand why this phenomenon is present, considering that Rasulullah (saw) and Ali (ra) were located in Madinah, and the first and the best Muslims were in Makkah and Madinah. How did it become so that the true Muslims shifted to Iraq and Iran and the deviant Sunnis became the dwellers of the city of Rasulullah (saw) and dwellers of the city of the most holy site in Islam?
Update: Saudi Arabia came into existence around the time my grandfather was born.

Shiaism, according to you guys, came into exitence around the time of Rasulullah (saw).
Update 2: *existence
Update 3: I know there are some Shias in Madinah, but since Shiaism is the true form of Islam (right?), Makkah and Madinah should be DOMINATED by Shiaism and the "Wahhabis" should never have been able to enter.
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