Or it was a trap, I don't know
It could be , lets see .
What did they get out of it ?

Taliban largely screwed and focused elsewhere...
Saddam gone...
America tied down...
America with a huge and growing debt...
Americas army strained...
Bush looking like the idiot that he is...
International consensus after 9/11 splintered...
Severe doubts over intelligence cliams on WMD development...
An increase in anti-western feeling throughout the region...
A new excuse to clamp down further on dissent at home...
A massive increase in the value of their commodities...
An opening for bigger legal and illegal trade...
Their friends in power in Iraq....
The oppertunity to kill their enemies in Iraq...
Wider regional alliances(including with states who quite frankly hate and distrust the mullahs in Iran)...
A nice training ground for the revolutionary guards and their apprentices....

The list could go on and on .
Perhaps it wasn't a trap, perhaps the Iranians just got really really unbelievably lucky .