Well, much of what is happening in Syria, and what has been happening in Iraq as well, has been a regional power struggle between Iran and Saudi Arabia. The fault lines have been the Sunni-Shia divide. Clearly, the Assad regime would have collapsed had it not been for the intervention of Iran and of Lebanon's Hezbollah.
I think that once Assad crossed the “red line” in using chemical weapons and there was no western military intervention forthcoming, it was a profound turning point. Now, of course, the Free Syrian Army is disturbed that the only time there is western military intervention it's in favour of the Assad regime.
I think these contradictions have to be understood, and there has to be a wider rapprochement between Iran and Saudi Arabia if there is any meaningful solution to the regional problem.
Lastly, the Assad regime is of course essential for Iran's ties with Lebanon's Hezbollah and the wider balance of power between Iran and Israel, so all of these pieces have to somehow fit together.