Is religion the primary motivation and recruitment behind ISIS?

People join ISIS for clear religious goals

Question: Is religion the primary motivation and recruitment behind ISIS?
Position1 of 2›: Yes, religion is the primary factor.
Argument‹2 of 2: People join ISIS for clear religious goals

The Islamic State's ultimate goals are centered around returning to the ideals of Salafi/Wahhab Islam.

The argument

The Islamic State is centered around Salafism, a conservative interpretation of Sunni Islam, with its roots in Wahhabism, another conservative interpretation of Islam currently championed by the Saudi Arabian government. The modern reformist Salafi movement is critical of what it deems as misguided practices of Islam and ISIS should be interpreted as a corrective effort within Wahhabism and a violent rejection of the official Wahhabism doctrine of the Saudi state. Hence, with its former leader Abu Bakr al-Baghdadi declaring a "caliphate" across Iraq and Syria on June 28th, 2014, ISIS seeks to establish a formal state that embodies the return to the true origins of the Saudi-Wahhab project.

Premises

[P1]The Islamic State is built on Salafism, a conservative interpretation of Sunni Islam rooted in Wahhabism, and presents itself as a corrective effort to return to the "true origins" of that project. [P2] Its declaration of a "caliphate" across Iraq and Syria shows recruits join in pursuit of clear religious goals—establishing a state that embodies that doctrine. [C] Therefore, because people join ISIS for clear religious goals, religion is the primary factor in its recruitment.

Counter-arguments

The core reasons why ISIS has interpreted Saudi Arabia of straying away from traditional Wahhabism is due to its collaboration with the West. While one could argue that religion is the ultimate cause, politics is the main facilitating factor that causes ISIS to act.

Rejecting the premises

[Rejecting P1] A doctrinal lineage explains the organisation's self-presentation, not what draws recruits; the premise describes the leadership's ideology and treats it as the motive of everyone who joins. [Rejecting P2] Declaring a caliphate is an act of state-building as much as of religion, and the counter's point is that the stated grievance — Saudi collaboration with the West — is political; the argument offers no evidence about recruits' own reasons, which is what the question asks.