The majority of Syrian people are sunni muslim, the same as almost all al Qaeda/Muslim Brotherhood-linked groups. The Assad family are alawite muslim, which is an offshot of shi’a islam which is what you see mostly in Iran and some parts of Lebanon/Syria. The alawites are a minority in Syria and like Christians, Assyrians and other minority groups will be exterminated when the sunnis take over.
The Iranians are supporting Assad against the Sunnis. If we just stay out of it, we might see the Iranians and al Queda expending themselves fighting each other instead of fighting us.