The unfortunate part is that they are just intelligent enough to be dangerous.
Most have psychological issues who come here...and Islam will do that the deeper one gets into it. Intelligence has no thing to do much with brainwashing....for some it's just a matter of degree they will go. But the majority in ISIS are followers and young men...easy to manipulate when they're already pre-programed in to Islam teachings...they jump quick to join...then their parents and family members will support ISIS because of fear for their child involved with them.