Originally Posted by _SpeedRacer_:
“But if Brody was set up, surely Javadi's boss would know about that...”
The Langley bomb was Nazir's plan with the Iranians from the start. Nazir used Brody to kill the VP so that there would be a mass gathering of intelligence officials, which would otherwise have been very unusual. Even when Nazir died, he knew he had done his part and the bombing would be able to happen even without him.
Javaidi/Akbari knew Brody wasn't directly responsible for the bomb hence Akbaris suspicion when Brody arrived in Tehran. At that point he had Javaidi vouching for Brody (otherwise Brody would have been killed at the Border or in the interrogation room). He used Nazirs widow to try to suss Brody out and Brody passed this test too. No doubt they also saw the video of Brody taking responsibility for the bomb. Irrespective of who the Langley bomber was, the US public thought it was Brody hence Brody was a propaganda coup who they wheeled out for the cameras in no time.
Any "enemy" of the US would be a "Big man in Tehran" especially give the fact he is Muslim and known pals with Abu Nazir, a known pal of Akbari.
That's how I saw it anyway