Most of the muslims in the West are sunni. They are not aware that shia even exists. Shia is the blood schism of muhammed. So when muhammed died, his sons wanted to carry on his legacy as the inheritors of his throne. Muhammed was red haired which means he was not Arab. His generals plotted against this and conspired to kill off his heirs. I forget some of the details, but the Arab centric generals won. His family and the shia schism fled to Iran from what I can remember. Been 16 years since I've had to study this stuff so I can't remember all the details so I probably got a lot wrong.