The Syrian war started with peaceful demonstrations with people calling for democratic reforms. So did the Iranian revolution.

It is possible to speculate that armed military involvement by former colonial powers in Syria might have led to the existing regime being overthrown, and its replacement by a democratic regime. However it's as well to remember that that was what was argued in the case of Iraq - it was claimed that the end of Saddam's regime would be greeted as liberation, and that an Iraqi democracy would be established.

Is a repressive sectarian regime better than a repressive secularist regime?