Iran fucked it up by destroying sunni Shia relations in Iraq over time, absolutely ruining their relationship with iraq *immediately* after 1979, and then whispering sweet nothings into Hafez Al-assad's ear because he was an alawite (branch of shia) that got him fully on team Iran over Iraq (their relationship was already marred by political differences but that *really* did it in for them)
Shekelsniffers didn't like that idea at all...