There are about 1.6 billion Muslims divided into two major branches. The Sunnis are in the majority with between 80%-90%. Shiites are only 10-20% and are found mostly in four countries Iran, Pakistan, India and Iraq. We often hear that Iran is the greatest exporter of Islamic terrorism, and that may have been true twenty years ago because they supported Hezbollah which was most active in the Israeli Palestinian conflict. Today however most Islamic terrorists are radical Sunnis, When you hear about radical islamic terrorists they are most likely Wahhabist or Salafist Sunni Muslims.
The following was taken from Wikopedia https://en.wikipedia.org/wiki/Wahhabism
Today Ibn Abd Al-Wahhab’s teachings are the official, state-sponsored form of Sunni Islam in Saudi Arabia. With the help of funding from Saudi petroleum exports (and other factors), the movement underwent “explosive growth” beginning in the 1970s and now has worldwide influence. The US State Department has estimated that over the past four decades Riyadh has invested more than $10bn (£6bn) into charitable foundations in an attempt to replace mainstream Sunni Islam with the harsh intolerance of its Wahhabism.
Wahhabism has also been called “a particular orientation within Salafism”, or an ultra-conservative, Saudi brand of Salafism. Estimates of the number of adherents to Wahhabism vary. One of the more detailed estimates of religious population in the Persian Gulf is by Mehrdad Izady who estimates, “using cultural and not confessional criteria”, only 4.56 million Wahhabis in the Persian Gulf region, (compared to 28.5 million Sunnis and 89 million Shia).about 4 million from Saudi Arabia, (mostly the Najd), and the rest coming overwhelmingly from the Emirates and Qatar.. Most Sunni Qataris are Wahhabis (46.9% of all Qataris) and 44.8% of Emiratis are Wahhabis, 5.7% of Bahrainis are Wahhabis, and 2.2% of Kuwaitis are Wahhabis. They account for roughly 0.5% of the world’s Muslim population.
The majority of mainstream Sunni and Shia Muslims worldwide strongly disagree with the interpretation of Wahhabism and consider it a ‘vile sect’. Islamic scholars, including those from the Al-Azhar University, regularly denounce Wahhabism with terms such as “Satanic faith”.Wahhabism has been accused of being “a source of global terrorism”, inspiring the ideology of the Islamic State of Iraq and the Levant (ISIL), and for causing disunity in Muslim communities by labelling Muslims who disagreed with the Wahhabi definition of monotheism as apostates (takfir) and justifying their killing. It has also been criticized for the destruction of historic mazaars, mausoleums, and other Muslim and non-Muslim buildings and artifacts.
Khaled Abou El Fadl attributed the appeal of Wahhabism to some Muslims as stemming from: Arab nationalism, which followed the Wahhabi attack on the Ottoman Empire Reformism, which followed a return to Salaf (as-Salaf aṣ-Ṣāliḥ) Destruction of the Hejaz Khilafa in 1925; Control of Mecca and Medina, which gave Wahhabis great influence on Muslim culture and thinking; Oil, which after 1975 allowed Wahhabis to promote their interpretations of Islam using billions from oil export revenue.
Scholar Gilles Kepel, agrees that the tripling in the price of oil in the mid-1970s and the progressive takeover of Saudi Aramco in the 1974–1980 period, provided the source of much influence of Wahhabism in the Islamic World.