It is often said that Islam used to be a lot more diverse than it is today (in the modern era). What is the history of this diversity in the place of origin of Islam itself? Has this region been a center where multiple sects could flourish or has it been a center of orthodoxy?
Even today, there's a bit of divergence. Oman is a majority Ibadi country and has been for centuries. As for the big sunni vs shia split you're probably thinking of, there were various different kingdoms and sultanates of either demoninations. Sunni islam was still, however, the main denomination. As far as the more modern history of Arabia, it's been very homogeneous, Oman being an exception.