* There has been a dichotomy between the Sunni and Shia sects of Islam for centuries. There have been times when it has been violent, usually during a regime change. However much of the time it has just been a philosophical divide, much like Catholic/Protestant differences, which, incidentally, have at times been very violent and cruel, also.
* In Mohammad's time (PBUH) Christians, Jews and Muslims lived together, had their churches/synagogues/mosques in the same towns. They were all considered "People of the Book." Christians and Jews did have to pay an extra tax.
* During the Crusades, that still held, but as the invasions continued and the Sunnis and the Shiites joined to fight off the invaders, the Crusaders used many ploys to turn that philosophical divide into violence. Sometimes it worked.
In Saddam Hussein's Iraq, all the faiths were welcome. The Sunnis and Shiites disagreed, but non-violently. They did not bomb each others mosques. Their Imams debated the various views. There was an exchange of ideas, not gunfire.
* After Bush went to war in Iraq, suddenly factions were blowing up each others mosques. There were a number of articles that appeared, linking that violence to US false flags, but they were quickly moved to the want ads and off the grid.
* The Wahabi are like Christian Southern Baptists. The world will not be right until everybody believes the way they do. This leads to trouble.
* Iran is mostly Shia, but there are no pogroms against Sunnis as such, but US and Mossad spend a lot of time and money fomenting and supplying dissident groups to cause unrest and violence, which is then trumpeted in the press.
* One of the main reasons that Iran is targeted is that not only do they have oil and gas coveted by our oil barons, but they are working toward getting rid of the dollar based oil bourse and creating one of their own, possibly based on gold. There are a number of countries that are working on this and they are all under fire by the US and its cronies.
* So, as with most problems, it is all based on power and greed, exacerbated by promoting sectarian differences to violence, then using that as an excuse.
* Iran has not invaded anyone for centuries. I am sure they help people, especially neighbors, who are being persecuted. For that help, they are a "terrorist" nation. If we do the same thing, we are helping patriots. Remember, we were a key to the creation of ISIS, to "get" Assad out of power. We also work with Al Qaeda to remove him. That has now come back to bite us, but it widens the wars, and the profits for the MICC, so it must be, as Martha Stewart says, "A good thing."
* This is just a "once over lightly," but I hope it gives some perspective as to what is going on.