There is a mistaken view that Islamism is a relatively new phenomenon. It can be shown that it is only the word 'Islamism' that is new. Those that take the view that Islamism itself is new - whether they are moderate Muslims, practitioners of interfaith or Western Islamophiles - usually attempt to prove the point by simply highlighting those features of Islamism which were specific to the 20th century; even though the same biased sampling can be used to argue that, say, Christianity or democracy was a purely 20th century phenomenon by citing TV evangelists or digital voting in Parliament.
The deeply and essentially political nature of Islam goes back to Muhammad, the Koran and the hadith. That political nature never really altered during the next 1,400 years. Indeed, depending on which Muslim you ask, and when you ask him, Muslims themselves are likely to stress Islam's 'totalist' nature. Moreover, it is precisely that politics-religion fusion within Islam which hundreds of millions of Muslims think makes their religion superior to all other religions. Without that fusion, they would argue, Islam would simply no longer be Islam.
What has just been said about Islamism can also be said about Wahhabism. The latter too has its most direct and obvious roots in the 13th century. (Wahhabis themselves stress this 13th century link.) However, Wahhabism, like Islamism, really goes back to Muhammad and his Companions as well as back to the hadith and the Koran itself.
The bottom line, then, is that Islam cannot help but produce Wahhabis (or 'revivalists') and Islamists. It has done so since the time of the Prophet and did so for the next 1,400 years.
It is said that the Islamic Golden Age lasted roughly from the 8th to the 13th century. Despite that, the Islamic reaction had already set in well before the 13th century. In the case of Ibn Hazm, the Zahirite or 'literalist', the Islamic war against philosophy and science began in the 11th century. (Ibn Hazm was born in 994 and he died in 1064.) His personal Islamic battle was against any non-Islamic accretion to Islam; such as all forms of deduction, analogy and the imitation of authoritative masters (taqlid). All of which, up until his own time, various Muslim theologians and jurists had applied to the texts and the teachings of Islam.
By the 13th century, that Islamic war of attrition had truly set in and begun to destroy all free thought in the Muslim world. Ibn Taymiyah was the main offender; but there were many others. It is clear that Ibn Taymiyah is still seen as a kind of proto-Wahhabi - and the same can be said of Ibn Hazm 200 years before Taymiyah. Indeed Ibn Taymiyah can be called a proto-Wahhabi because Wahhabis themselves see him that way.
We can trace a line from Taymiyah in the 13th and 14th centuries to al-Wahhab himself in the 18th century; all the way from there to the rise of the rise of the 20th Wahhabi movement in Arabia and beyond; and then ultimately to Osama Bin Laden and al-Qaeda. Consequently, just as Islamism is not a new phenomenon (many see it as being as recent as the last few decades), so contemporary Wahhabism stretched back to the 18th century and back to the 13th century; and then, ultimately, beyond that to Muhammad and the beginnings of Islam itself.
As for Taymiyah (1263-1328) himself.
Considering we are speaking of a Muslim ‘philosopher’ who predates Wahhabism by 600 years, and 20th century Wahhabism and al-Qaeda by around 800 years (as well as the fact that some would place him within the Islamic Golden Age), it is interesting to note that he denounced all theological and philosophical methods of proof when it came to Islam and to Islamic texts. Instead, he demanded a return to the ways of who were then called - and indeed who still are - the ‘pious ancestors’ (al-salaf al-salif, from which contemporary Salafism get its name).
Muslims were also calling for a return to the ‘pious ancestors’ (as al-Wahhab did in the 18th century) in the 19th century. What this partly meant was that these 'revivalists' believed that all Muslims truly need, according to the Wahhabis and the Salafists, are the Qur’an and the hadith as interpreted by the Companions of the Prophet and their immediate successors.
Once those ‘interpretations’ have been decided upon, then that is final. It is said that the authority of the interpreters is confirmed by the consensus (ijma) of the community. However, many non-Muslims - and perhaps some Muslims - mistakenly think this means that all Muslims are involved in the ijma and that this is a democratic process of some kind. It isn’t. The community, or ijma, only refers to imams, clerics, etc. – not to ‘the people’ and certainly not to Muslim women or to non-Muslim subjects (i.e., dhimmis).
The upshot of this Islamic reaction - amongst hundreds of others during Islamic history - is that all consequent interpretations of Islamic texts were deemed suspect and frowned upon. The same was true of all further theological, philosophical and even mystical additions, developments and accretions to the Koran and hadith. In fact all such movements within Islam were deemed as heresies (bida). And to this day they are still classed that way by literally hundreds of millions of Muslims.