By the way
That Syrian revolution--do you remember how it started?
Removing Assad leaves the most organized and able group to take over--that is IS
On the other hand, letting Assad remain is no different than what has happened in several other ME states in which a dictator oppresses their people. There were already several filed civil wars because of our relationship with the rulers.
I doubt the Syrian civil war is a natural evolution of that state. Nor do I think its continuation is normal--who are the rebels and where are they able to get support to fight a war for more than 2 years against Syria and their allies(Russia and Iran?). Think about it.