It's this nasty habit of building empires. It's in their DNA, and it's hard to stop them. Let us ask some questions... why did they foster the Hezbollah? Because by the end of WWII, after Iran was the second muslim majority state to recognize Israel as a nation state (after Turkey), things changed. the US started to support SA due to oil, and Israel followed. One side declared the other an enemy, and the other responded by treating it as such (Axis of Evil speech, George Bush.)
In spite of thousands of years of peaceful co-existance with Jews, they now look upon them as their enemy. There are millions of Jews in Iran today, living without fear.
"The beginnings of Jewish history in Iran dates from late Biblical times. The biblical books of Isaiah, Daniel, Ezra, Nehemiah, Chronicles, and Esther contain references to the life and experiences of Jews in Persia. In the book of Ezra, the Persian king Cyrus the Great is credited with permitting and enabling the Jews to return to Jerusalem and rebuild their Temple; its reconstruction was carried out "according to the decree of Cyrus, and Darius, and Artaxerxes king of Persia" (Ezra 6:14). This is said to have taken place in the late sixth century BC, by which time there was a well-established and influential Jewish community in Persia. Persian Jews have lived in the territories of today's Iran for over 2,700 years, since the first Jewish diaspora when Shalmaneser V conquered the (Northern) Kingdom of Israel (722 BC) and sent the Israelites into captivity at Khorasan. In 586 BC, the Babylonians expelled large populations of Jews from Judea to the Babylonian captivity. Jews who migrated to ancient Persia mostly lived in their own communities."
But yes, they have this nasty habit. Of building empires. How they west decides to work with this trait might determine the fate of the ME.