Peaceful transition to what?
The area was already awash with jihadis who would have ridden roughshod over the civilians. Don't forget the Al quaeda/terrorists who had come over from Iraq etc as part of the isis push.
Assad holds the army together, without them it would be impossible to completely have stopped isis.
All of which happened a long time after the fighting started. Would isis even have had a chance to take hold in Syria had he stepped down rather than send in the tanks against his own people?
Anyway, it's off topic.