If the CIA prisoners at the Annex had been the focus, I don't think Woods and Doherty would've been asking permission two times to go to the consulate.
Stevens himself was more likely the reason, whether for hostage-taking, retribution, or to dissuade him from his mission to relieve AQ from their weapons. If the CIA was to be punished for their activities, it seems the Annex again would've been tops on the list of strike zones.
I think the attackers had scoped out the "consulate" as the place to "get" Stevens, given by whom it was being "guarded" and how easily those Brigaders could've been persuaded to help the AQ cause. (An absolute FusterCluck, Clinton!) If manpad recovery via buyback, I look for an 8- or 9-figure dollar amount to be onsite with Stevens and the the jihadis wanted all: the money, the manpads and to symbolically rub the Americans face in the mud via sodomizing the Ambassador, who--in a muslim newspaper, no less--had advertized to give security jobs to homosexuals! If Stevens didn't survive, "Too bad!" I'm sure they'd say.
If the jihadis didn't get the money the first night, they had three weeks before the FBI arrived to pick the place absolutely clean. What another degree of special for Zero not to have goven orders to secure the site when he had opportunity, 4:30pm 9/11/12, certainly before he left for his Vegas fund-raiser!
HF
Have read Zawahiri ordered the attack as revenge for the elimination of al-Libby.