To the Gulf States, Iran is the Great Satan. It is the heir to the ambitions of Persian rulers who did not make out that well.
Persia attempted to conquer the Greece city-states but failed. Alexander put them in their place.
We should never forget that Persians are not Semites but Aryans. Efforts at world domination were thwarted and Persia was under control of a Greek general after Alexander’s conquest was divided among his subordinates. Egypt would similarly become the domain of Ptolemy.
While Egypt went from Greek to Roman control, Persia became Parthia and inflicted much harm on Rome. Various dynasties flourished and fell. Invaders had their way.
Persian disrespect to diplomats sent by Ghengis Khan was rebuked with massacre and conquest but the nation was soon under a succession of dynasties. The last Shah was part of a short-lived dynasty. His efforts at modernization offended fundamentalist Muslims and he also had enemies on the left in the form of the Tudeh Party. With some covert help from the USA, the Shah became the center of power. He also cooperated with Israel in a number of areas and was aloof from most of the regional follies.
The Shah was opposed by the Left as well as by the radical Muslim literalists. His lack of support from President Carter assured his downfall and Carter was soon to follow.
The Mad Mullahs are an irrational lot and were seen as a regional threat. They are opposed by those who grew used to Western ways along with the hard left. Politics is rigidly controlled and no true opposition is tolerated.
What interest does Iran have in Lebanon other than to stir up trouble and hope that Iranian influence in the region will evolve into control?