More at the source including diagrams
oops forgot link
The big split in the arab world is the split between Sunni and Shia, and Iran does fish in those waters.
Now, since Sunni tend to support Al Qaeda and ISIS, and Shia tend to support Shia militia movements, deducing who are the good guys is tricky.
Is it better to support Bahrain, where our Navy docks, against Shia militants? Would a Shia Bahrain support our operations there? Iran seized two islands from Dubai, so Dubai has issues with them. On the other hand, Dubai has always helped Iran to trade despite sanctions, so Dubai is actually pretty close to Iran. Figuring out who are the good and bad guys is pretty tricky.