I think your claim about westerners and foreginers are besides the point in some ways, these people are the outliers that the media fixates on, but the real core of these groups are local/domestic young men and women who have little else to do or hope for in their countries or communities. I think that ISIS/L is tapping into and directing a sense of futility and purposelessness and rerouting those tendencies into an organized social system. I agree that money is not the only thing but it absolutely counts, especially when you look at the unemployment numbers in the region.

Below are some of the characterizations from the article that support my idea that terrorists are compelled to do terrorism because they lack the means to do anything else meaningful with their lives:

They were searching for meaning in their lives

Recruiters promised them glory, adventure, and purpose – things that appeal to many young people.

...that it is possible to create a utopia.

...defending your beliefs

ISIS ... is adept at leveraging idealism

... recruiters often spend hundreds of hours showing young people how the problems they see in the world and in their own lives are connected to larger problems

Terrorists believe they are making the world a better place

Overall, these are the characteristics of purposeful, employed people who are working. Terrorist recruiters are tapping into a singular void of lack of mobility, lack of purpose, lack of work. They feed on the vacuum that gainful, purposeful work would occupy in a less ravaged, more civil world, one with opportunities. Since there are barely any opportunities, then terrorism becomes the de facto "next stage," much in the way that a college education, or military training would predicate gainful employment in more balanced societies.