Lots of people have big ideas. Few can competently execute on them. This is true of commercial entrepreneurship and international terrorism alike. From what I can tell, ISIS is (or was) unusually well run [1].
[1] http://m.spiegel.de/international/world/islamic-state-files-...
Well, of course they are. American Green Berets ran an extensive "train the trainer" programme in Afghanistan, bootstrapping the precursors of the Taliban into a military that could take on the Soviets.
Then once the Soviets were gone, the factions turned on each other, which meant, they continued to practice and refine what they have learned. An ISIS equivalent of a Drill Sergeant probably isn't too different from his Western counterpart...
It's not obvious exactly why the IS is different, but I doubt it has anything to do with American influence. Other rebel groups in the Syrian civil war has had direct American training but they were highly undisciplined and ineffective.
The real origin of ISIS's organizational skill is the disbanding of the Iraqi military in 2003 - a totally unnecessary decision on the part of the US that played a big part in the ensuing chaos in the country. Lots of military officers from the old regime, disproportionately Sunni, out of a job, and none too picky about the specific ideologies of the groups that would advance their sectarian interests, transferred their knowledge to groups like AQI, the ancestor of ISIS.
So not only the military knowledge, but the people that know how to run the factories and the people that can handle the logistics of such a thing. Not to mention teachers, medical staff, and similar posts.
Which was inspired by the denazification effort in post-WWII Germany. The problem is that the U.S. actually tried to follow through this time (the denazification effort rather notoriously slowed down first as the Allies realised that they needed competent administrators if they didn't want the Germans to starve to death, and then later as the Cold War heated up).
In retrospect the U.S. probably should have deliberately chosen to prosecute only the bigger fish, with a ban from public employment one punishment for the smaller of those. But hindsight is 20/20.
Then why didn't they clearly see the problems that happened when they tried this is Germany and Japan?
Our experience in Iraq indicates that perhaps the Pragmatic Thing can also sometimes be the Right Thing. We might have been able to avoid a lot of injustice with a relatively small amount of injustice.
I think one of the reasons that 'these people' aren't frequently over-estimated (or even accurately estimated) is because almost none of them have higher education from their own countries.
Not that many higher education facilities have a specific 'learning from your enemy' track, and it's not as though there are respected rules around not using your enemy's facilities against them ... but you know what I mean.
0. https://en.wikipedia.org/wiki/Slat_armor and https://en.wikipedia.org/wiki/Spaced_armor
Well post 1990 or so you use diagrams on complex weapons because you never know when you'll want to MANPADS (which are fairly complex as weapons systems go) to a bunch of farmers.