One topic alluded to, but not directly addressed in this conversation is education.
The Catholic Church, in its heyday, as is Islam still, was taught be a few educated clerics to the uneducated masses. The Mass's only source of information was their local cleric as they could not read for themselves. In Christiandom, Martin Luther rebeled to this top down theocracy, as my governments were vassels of the church just as were the masses. Once people became more educated (literate) on a individual basis, they found that what the church was teaching wasn't necessarily correct. Thus the revolution and proliferation of Protestant (I protest) churches.
Islam followed the same path with clerics teaching their own ideas or interreptations of the holy word of the Koran. The Mosaic laws of Chistianity, and eye for a eye, etc, was greatly expanded upon in the Koran and became the basic legal framework of the governments of Islamic nations just as the Mosaic laws became the basis of most of the christian worlds legal framework.
The major difference is that as Christiandoms dictate of religon was being rent assunder, the Islamic clerics hold over the masses was becoming more deeply entrenched as education was claimed the right of the church, hence, a conserted effort was made, and is still being made, to keep the follower of Islam illiterate, education was(is) done orally. Today's Muslum has been indoctrinated to believe that the word of the Koran, as interrepted by his local cleric, is the word of God (Allah). This indocrtination (read brain washing) has, over the centuries, resulted in a group of fanatics.
It could very well have happened in the opposite way, with Christiandom becoming the fanatics and Islam the home of literate scholars.
In the United States, most Muslums, were either those who chose to become literate, hence prosperous, or have become so after coming to this country. Either way, their enlightenment through literacy has caused a moderating of their zeallousness. In the Arab countries, where only the elite have become iterate, thus less zealous, the illiterate masses, still being dependant on the oral teachings of their clerics remain the fanatics.