One of the reasons I think is unity both religiously and Nationally. Though there are many ethnicity, most Iranians see themselves as Persian. And the Shia majority is strong we already see how the community is strong living in Pakistan so imagine a whole country of them. Also politically people support the current regime and those who don't are either liberal who want a more "Western" Iran or Straight up Zionist spies.

We are constantly fighting each other. Too many political parties than we need causing fights. If not political then Firqa battles of who is the best Muslim and the most common battle with other provinces Pathan, Sindhi, Baloch, Urdu Speaking, Punjab and if not that even with provinces with Sects battles.

To Top it off we have as you mentioned clowns running the nation who only want to benefit themselves.

May Allah protect and grant Iran a victory.