Criminals
Visualizing these people as ordinary criminals, instead of an army in a cultural war, is a mistake. There is a wide network of religious-based educational and financial backing for these groups, based in the Middle East and elsewhere, and this is only one piece of the whole puzzle. This isn't a series of unrelated crimes. This is a war.
If Al Capone had been running universities to train thousands of gangsters all over the world, your analogy might be a bit closer.
Canada used internet and phone monitoring to catch these guys.