That's the title of a piece in Slate by Tim Harford. The focus is really on the background of terrorists, which turns out, according to one study, to be well educated, particularly in comparison to the milieu from which they come. The British doctors involved in the last attempts are an example. All of which accentuates the question--why is someone who is smart enough to get an MD incompetent as a terrorist?
My answer is --first, you never get it right the first time ("Harshaw's law"). Second, the brits seem to have been operating without close guidance from more experienced terrorists. (The Palestinian suicide bombers had a whole infrastructure in place. Even though the bomber was a first (and last) timer, the organization was not. Third, terrorism is probably harder than it seems from the outside.