Sounds like the SFA is kind of a small force and that Assad has Damascus in a tight grip. Is the SFA attempting to establish a separate state in Aleppo?
It's one of many possibilities - (1) they assassinated four bigwigs, and believe the high command is in disarray and the regime only needs a nudge to collapse, (2) they are getting picked apart piece by piece and need the regime to focus its efforts in one area so that they can regroup elsewhere, (3) they need to show progress in order to get their foreign funders to continue ponying up cash, (4) they have the regime on the ropes and see this as the death blow or (5) they are being a little impatient and have decided to bet it all on one roll of the dice. My guess is that it's a combination of 1, 2, 3 and 5. I think Assad will get this cleaned up pretty quickly because he is willing to do the one thing that works well in countering insurgents - massacring the civilians providing logistical support for them (whether out of sympathy for their cause or coercion). The Mongols are probably the most notorious example, although the Nazis came pretty close - guerrilla warfare was a minuscule problem in Nazi-occupied Europe, although not as insignificant as it was for Mongol-occupied lands.