I am learning about the Sunni/Shi'a conflict now, and the fact that this major sectarian divide is caused by a power struggle thousands of years ago seems too simplified to me. Are there other reasons why this divide is so large, such as prejudice, war, strife and religious difference?
I would like to add, how much of the modern Sunni Shia divide in the Persian Gulf region (with full understanding that South Asia, the Levant and parts of the Gulf have large non-Persian Shia populations) is an Arab-Persian divide?
/u/Kiviimar talks about the evolution of the Sunni/Shia split here