From my experience I have to say that those people arent stupid. They are geniuses. Masterminds! They get everyone to do their jobs or explain all to them cause they look so "helplessly stupid". They make their coworkers (rivals) get mad, frustated and distracted from their work in many ways.

The peak of those masterminds are the young pretty girls mid 20s-30s. Bosses look at them as if they were some kind of adorable puppies and cant imagine the real evil that lurks behind those "innocent" minds. I may be biassed here cause I lost to one of those and made my life hell for a few months.