I remember watching a really interesting documentary about the rise of Islamism (political side) and Jihadism (the military side).
It basically states how for decades (going back 50-60 years) the Saudis with their oil wealth offered to fund the building of thousands of mosques around the world including in Islamic communities in the West on the condition the mosque's Imam (muslim cleric/preacher) was trained in Saudi Arabia and/or learnt the Wahabbi/Salafist strain of Islam the Saudis practised. For those of you who don't know what Wahabbi/Salafist Islam is, think 7th century Islam. Islam in all it's pure unadulterated form. It was taking place during the Cold War so went mostly unnoticed and after all Saudi Arabia was a major US ally and under her security umbrella as well as a major investor in the US economy including recycling it's petrodollars into the (but not limited to) US arms industry. So for decades the Saudis quietly were spreading their strict brand of Islam to a large segment of the worlds Islamic population.
What really caused the rise of Jihadism (the violent side of Islamism) was the Soviet-Afghan mujahadeen conflict of the 80's (79-88). The US was determined to give the USSR their own Vietnam and with the help of her allies most notably Pakistan (secret service) and Saudi Arabia (money & jihadi fighters such as OBL) they did just that. Most of the money was being funneled to the most extreme jihadis since they turned out to be the better fighters and they were closer ideologically to Zia ruled Pakistan and Saudi Arabia. Unfortunately all this would come back to bite all three countries in the ass years later. Pakistan because it sided with the US on the War on Terror and Saudi Arabia because it used American troops to oust Iraq from Kuwait quickly rather than volunteer Islamic mujahideens in a long drawn out guerilla war ala Afghanistan. The Islamic extremists turned on their former benefactors as traitors to Islam and vowed to topple them and replace them with an Islamic Caliphate.
Another issue is oil has been a curse as well as a blessing to the region. From outside interference to internal political repression, Saudi Arabia prefers to rely on expats doing all the work while they keep their own citizens ignorant and bribe them with a cradle to grave state support system. But while Saudi Arabia has been effective at rooting out Jihadis from it's country, it's still preaching the same Wahabbi Islam in it's schools and mosques. In fact if anything Wahhabism has grown even stronger in Saudi Arabia with it's proponents bulldozing historic Saudi sites for fear it will lead to idolatry. They even have Muhammad's tomb in their sights.
