Perhaps Nick was on his own "secret mission" to make peace with Al Queda and ended up in a bad trap.
Its difficult seeing an average American running off to Iraq on their own...with no introduction...no connections...etc. I think Nick had a connection...and it wasn't your friendly neighborhood type...it was a Muslim group who he thought he could trust. Nick probably found out it just was not the kind of group to hand out with on a Saturday afternoon...but it was too late.
I think your on to something. Elsewhere and acquaintance reportedly said that he had made lots of money, enough for a jaunt through Turkey.
I think his Islamic acquaintances set him up, and delivered him to AQ. A young, idealistic, non-conformist American must have seemed an easy mark. Throw him money for some "contract" and reel him in. I wonder if they got their money back, and how? Paper trail?