Are they that stupid?

The Canadian police and security forces recently arrested 17 young men, city dwellers, educated, mostly of Arab descent, who had ordered and either received or were about to receive three tons of the very same fertilizer-based, explosive material that Tim McVeigh had used in Oklahoma City. This news is both frightening and relieving. Frightening in that the alleged conspiracy got as far as it did, but relieving because they were found out and stopped. There's just one more thing though, looking away from the matter of fanaticism and radicalism for a moment, how could anyone that is obviously not a farmer be so stupid as to order three tons of a material that was a well known explosive? And how could a fairly large group of people from an ethnic group that is obviously being targeted by surveillance be dumb enough to think that they could pull this off? Not to be alarmist, but isn't it possible that these guys were trying to get caught? And if so, why would they do that? In order to be decoys? In order to test how quickly they were going to be found out? In order to fail and thus not have to die for a cause that they may have started to doubt? Maybe even in order to fail and not be vulnerable to reprisals from their former handlers? It seems as if there are many possibilities there, and I hope that people who know their stuff in this regard will look at it from those angles as well. Because it just seems a bit implausible that there is nothing more to this story than what we have heard so far.