You can't cross the Arabian peninsula to the Red Sea either as there's also a mountain range on the west of it.

The only viable passage would be through the center of Oman (no mountain here) but that would be a gigantic canal. And that wouldn't really solve the issue, as the Iranians could easily block the canal as long as it is within reach of their drones and ballistic missile: you just need to hit one ship in the canal to effectively block it.