Why is Persia now called Iran? - yes, all because the name was given by the Greeks, and the people living in this country, since ancient times, have called it Iran, that is, the country where the Aryans live. It turns out that the country was named by the ancient Greeks as Persia, and after them other peoples adopted this name and transferred it to the whole country. The name comes from the Fars region, which is located on the shores of the Persian Gulf. Earlier, the Achaemenid Empire was formed by the peoples who lived here in the middle of the 6th century BC. It was for this empire that the name Persia was assigned. And then for the state of the Sassanids, who became followers of the Achaemenids.
Today, people living in this country call it Iran. Namely - the country where the Aryans live.
For the first time, Reza Shah Pahlavi demanded to call Persia Iran, in 1935. One of the many versions is that the Iranian ambassador, who in Germany fell under the influence of the Nazis, pushed Reza Shah Pahlavi to change the name. He argued (in the opinion of the Germans) that the name Iran would emphasize the fact that the inhabitants of the country are of Aryan origin.
But, a few years later, Iranian scientists began to object, and put forward a version that the country, thus, will lose connection with its historical role. The result of such actions was that in 1959, Shah Mohammed Reza Pahlavi gave permission to the international community - the opportunity to use both of these names in parallel.