It could be more than one thing going on at Benghazi....MANPAD recovery may have been a screen for a couple other things. It’s a LOT of people for a relatively insignificant city.
Relative to what..? Bengazi is only second to Tripoli in Libya. And for very long East Libya was it's own Emirate, with Bengazi overwhelmingly in control of it.
Bengazi already had been a focal point for Islamic kooks in North Africa for quite some time --Bengazi was the Animal House of both kooky and spooky. It was very, very much on the CIA's radar-screen.
Regarding your point that there was probably more than one card in play in Bengazi, well there, yes I do believe you are correct.
I believe the main thing was the missiles, however I think probably there is some other major matter that they want to shut folks up about that had been going on, there.