From Reddit (source ):
Summary
(1) Qur’aan directs one to the Sunnah as the secondary source of the Deen.
(2) Sunnah shows a report stating that the righteousness decreases through the generations, and also records the reports of the Salaaf only, since the reports were compiled in the 3rd generation.
(3) In 13th century, ibn Taymiyyah said that all the Muhammadian scholarship from the 4th generation was corrupt, and one had to follow the Salaaf on all matters.
(4) Though ibn Taymiyyah was jailed for forming a cult, he wrote books while in jail.
(5) Then in the 18th century, the Arabs were unhappy with the Turks for heading the Muhammadian Khilaafat under the Ottoman Empire.
(6) Then, Abd al-Wahhab revived ibn Taymiyyah’s teachings and said that the modern Muhammadians had innovated, and he promised to restore the Muhammadian world to the way it was in during the time of the Salaaf-s.
(7) During the time of the Salaaf-s, all rulers were Arabs, so he proposed the Arabs should rule.
(8) To make his vision a reality, he took the help of a local tribal warlord, Muhammad bin Saud, to clean Arabia of non-Arabs, modernity, and anything not Muhammadianity.
(9) While Muhammadianity preaches against hereditary monarchy, Wahhabism promotes it, as long as the ruler is a Saud.
(10) Back in the day, the Ottomans loved Muhammadian arts so much that they refused the Qur’aan to be mass printed.
(11) So the Qur’aan was mostly mass printed in Europe more than the Muhammadian world - mainly in UK.
(12) Meanwhile, the Wahhab-Saud duo took weapons and training from Britain, and began to mass-print ibn Taymiyyah’s works.
(13) This teaching to non-Sauds required a new tactic - since they had leaders who were not Sauds - which became Wahhab-ism 2.0, or modern Salaaf-ism.
Wahhabis and Salafis (they’re similar movements, but not exactly the same) are still Muslims (kind of), they’re just revisionists who have reinvented Islam to make it seem like their Islam is more authentic (which it isn’t). To understand this, I’ll outline the origins of Salafism, how Wahhabism grew out of Salafism, and how modern Salafism grew out of Wahhabism. The terminology is going to get confusing because there are at least two groups that use the “Salafi” label and differentiating them can be a headache.
So there’s this sahih (authentic) hadith appearing in Sahih Al-Bukhari (Hadith 8.686): Narrated by Zahdam bin Mudarrab ‘Imran bin Hussain said, “The Prophet said, ‘The best of you (people) are my generation, and the second best will be those who will follow them, and then those who will follow the second generation.” Because of this hadith, Muslims since the time of the prophet have always looked to the idea and methodologies of the first three generations of Muslims, who we call the Salafs. The Salafs were not static; while they followed Islam as taught to them by the prophet, they also had to be adaptative to new circumstances as they appear. Consequently, the Salafs lefts us with a legacy of a constantly evolving Islam wherein each generation would keep that which the previous generation had taught, and build upon it, always being guided by the examples set by the Salafs.
Some time around the 13th century, however, an obscure Muslim scholar by the name of Ibn Taymiyyah proposed that all Islamic scholarship from the 4th generation onward was corrupt and that while the Salafs might have built upon the knowledge and teachings of the prior generation, that process should have ceased by the 4th generation. Needless to say, Ibn Taymiyyah’s ideas didn’t sit well with his contemporaries. Not taken serious as a scholar, Ibn Taymiyyah took to preaching his ideas to the less educated laity, which won him something of a cult following in the 13th century. His deviant teachings and the militancy of his followers upset the Caliph of the time, who subsequently had Ibn Taymiyyah jailed as a heretic. Nonetheless, Ibn Taymiyyah continued to write and preach from his jail cell. Nevertheless, Ibn Taymiyyah’s writings were not taken seriously by more learned Islamic scholars and his works would eventually fall into obscurity.
Fast forward to the 18th century and the Arab world was no longer the seat of power in the broader Islamic world. A Turkish Ottoman sultan was the caliph of Islam and the Muslim empire stretched from S.E. Europe, through Asia, the Middle East, North Africa, and parts of southern Africa, the Indian subcontinent, and S.E. Asia. The Arabs, who had once held themselves to be the most important people in the Muslim world, had lost their special status. Moreover, many of the Ottoman appointed administrators in the Arab world were not even Arab, they were either Turks or Jews. This led to an event that historians have dubbed the “Arab Revolt”, which was an Arab nationalists movement aimed at toppling Ottoman colonial rule and reinstating Arab power or Arab supremacy within the Muslim world. The problem, however, was the Islam doesn’t allow for rebellion against a legitimate ruler. However, another obscure Islamic scholar had just returned from is studies in Basra (Iraq) to his home in Arabia, and this obscure cleric, inspired by the works of Ibn Taymiyyah, proposed to rid the Muslim world of any and all innovation to get it back to how it was in the time of the Salafs. And of course, none of the Salafs or caliphs in this period were Turks, they were all Arabs; therefore, he proposed that only an Arab should rule. This obscure cleric was named Muhammad ibn Abd al-Wahhab. And to help make his vision a reality, he teamed up with a local tribal warlord, Muhammad bin Saud, to cleans Arabia of non-Arabs, modernity, and anything not “Islam”. The legacy of “Wahhabism” is that while Islam preaches against hereditary monarchy, Wahhabism promotes the idea, so long as the monarch is a member of the Saud family.
Of course, the first Saudi state failed and the Ottomans eventually reclaimed Arabia. The Wahab-Saud partnership, however, didn’t die with the state. One of the major flaws of the Ottomans was that they so loved Islamic arts that they refused to allow for the Qur’an to be printed with the printing press. In fact, they didn’t allow for any Islamic reading materials to be printed with a printing press, instead preferring that all Islamic reading materials be meticulously written by calligraphers. European powers had had a long and complicated…most hostile…relationship with the Ottoman Empire for centuries, and the emergence of an Arab revolt against Ottoman rule was something they could exploit. Moreover, the Wahab-Saud duo, while bad mouthing non-Muslims all the time, were more than happy to accept help from the British in the form of guns, explosives, military training…and access to the printing press. In the 19th century, most Qur’an and other Islamic reading materials were mass printed in Europe (esp. the UK), not in the Muslim world. The Wahab-Saud partnership also asked the British to mass print the works of Ibn Taymiyyah for distribution to other Arab leaders and tribal warlords to help grow the Arab nationalists movement against Ottoman rule. This teaching of “wahhabism” to non-Saudis required a different tact; afterall, non-Saudis had their own sultans or tribal leaders, so reverence for the al-Saud family was omitted from Wahhabism 2.0, which we now call…Salafism.
Modern Salafism claims to be following the Salafs, but ignores that fact that the salafs appear to have believed in an ever evolving Islam that had to be adaptive to new situations. Modern Salafis are also known for their extreme conservativism, propensity toward violence and fits of rage, moral policing, and manner of dress that sets them apart from the bulk of the Muslim world. Modern Salafi teachings, while borrowing heavily from the heretical writings of Ibn Taymiyyah, also draw many of their teachings from Khawarjism, which is why the overwhelming majority of Muslims to rushed to join ISIS were Salafis.