The central tenant of traditional Sunni Islam is to follow the Ummah, the community. This has lead to alot of diversity as basically any Imam leading a community will inevitably make changes. Kinda why you have Muslim countries that will beat the shit out of a Muslim for drinking and others that have a drinking problem.by radical, you must mean "openly muslim" because Islam is a monolithic religion.
Honestly, I'd trace radical Islamism from western countries to the Quran being fucked up, Saudi funded mosques and social autism. A high % of engineering students joined ISIS and engineering students have a higher % of autism. They were disconnected to their community - opted for the Quran or internet and became extremists.
if anything, Islamic extremism in the west has the same roots as lolcowism and other sorts of extremism.