Why should this be the "most controversial theory"? Have we already forgotten what triggered the Arab Spring, and consequently the power vacuum that created the IS?

The only thing off, as far as I can tell, is the remark that "economic deprivation and the horrors of wars [...] benefited only a select few of the region's residents." I'm not sure if this is the WP mis-reading Piketty, but he makes it pretty clear in Capital that war benefits no one, especially the super-rich. It's not like the Arab aristocracy were itching for multiple revolutions that called into doubt the existing power structures.