I no longer care why they "slip into jihad". They do so because they are promised things that appeal to them more than doing the right thing does.
It's important to understand it, though. Note that the standard, "oppressed and poor" trope often seems not to apply to these guys. How many times have we seen bright, young engineer/doctor/astronomer types "slip into jihad?" The story usually goes that they are smart, idealistic types who grew up in an insular and intolerant culture with strange ideas about women, and fell prey to homicidal doctrines preached by an evil Imam.
In a normal culture, these guys wouldn't dream of mass murder. Western culture for various reasons -- not all of them bad -- wants to avoid naming the obvious: that there is a toxic brand of Islam, much as there is a toxic brand of white supremacist Christianity, or murderous sects of Hinduism.
Failure to name it, and failure to shine a light on the idiocies it preaches, is the worst possible thing. And that's precisely what the left in Europe and elsewhere have done. (Then again, there's a distinct whiff of the 3rd Reich among some who do name it....)