Many Muslims are subject to extreme indoctrination and brainwashing regarding the metaphysics of martyrdom. Jihadist imams have figured out the virality of this particular meme, and the environment in which it may take root.

Depressed economic conditions end up gifting jihadist recruiters with more reasons for individuals to join up and become a martyr.

The biggest issue is the believe that there is a separation of "extreme islam" vs "mainstream (non-violent) islam" when the calls for violence in the religion are extremely clear and in their holy book: https://www.youtube.com/watch?v=4LBpmPXv1R4

> Why does this group of Muslims kill people while the vast majority do not?

Pareto?

https://en.wikipedia.org/wiki/Pareto_principle