My understanding of the current tensions is that a large part is due to the way borders were set.
Similar to African nations, once the colonials wanted out of the Middle East (as colonial authorities so to speak) the nations were carved up along colonial lines rather than ethnic/tribe/religious lines.
Different to western nations, at an individual level middle eastern individuals put religion as being more important than nation. Family, religion, state. In the west it's family, state, religion. Generally.
Now this carve up in the Middle East is either fascinatingly stupid or fascinatingly advantageous from a western perspective. It's stupid because you ended up with very unstable countries made up of Sunni, Shiite and Kurds battling to get along and take power. This creates uncertainty and with this comes civil war, pressure on democracy etc etc. But advantageous to the west because a country isn't strong enough to be pulling in the same direction it leaves them prone to the west raiding them for resources. It was almost destined to be this way, short of everyone dropping arms from day one and loving each other like their own.
Syria is an extension of this.
Of course there are more factors at play but this is one of the fundamentals which I don't think is properly understood.
Also, a factor not well understood in the current Syrian crisis is the fall of Libya. As I am understand Libya was going to float its currency on non-US dollars which is problematic from a western/US perspective as to how the global market is run to benefit the west. Hence the US intervention via various means including the Arab Spring and weapons on the ground and a new leader was implemented. Problem is, thousands of weapons were then sold by various groups within Libya to generally anti-western forces in Syria.
