https://quillette.com/2024/01/04/why-iran-is-the-key-to-peace-in-the-middle-east/
Prior to the Islamic Revolution of 1979, Iran and Israel had developed strategic and economic ties, driven in part by Israel’s “periphery doctrine”—a policy of seeking alliances with non-Arab states. The relationship between the two countries was mutually beneficial; Iran was a major importer of Israeli arms, and, in return, provided Israel with oil. For the three decades preceding the revolution, these amicable relations persisted. Israel even had a diplomatic mission in Tehran.
The Iranian Revolution changed all that. Under the new theocratic regime, Iran labeled the United States the “Great Satan” and saw Israel as the “Little Satan.” The mullahs aligned themselves firmly with the Palestinian cause and against Israel. This shift was marked by calls for solidarity with the Palestinian people, the establishment of Quds (Jerusalem) Day, and the creation of the Quds Force, an elite unit of the Islamic Revolutionary Guard Corps (IRGC), whose ultimate goal is one day to capture Jerusalem.
The Islamic Republic’s apparent commitment to the Palestinian cause was, in reality, a strategic move designed to bolster its revolutionary credentials among Arabs and across the Sunni world and further its efforts to its Islamic Revolution beyond Iran’s borders—a task rendered more difficult by the fact that Iranians are non-Arab and are Shia, rather than Sunni, Muslims.
Iran’s ambitions in this regard were hampered by Egypt’s peace treaty with Israel in 1979 (and later by Jordan’s in 1994.) Tensions between Iran and Israel increased after Israel invaded Lebanon in 1982, with the aim of attacking Palestinian Liberation Organization targets, following the PLO’s attempted assassination of the Israeli ambassador to London.