I think that most of the people who have been featured here shared the same propensity for being stupid because they all believed the same crap that got them dead.
Officially it's called the Dunning-Kruger effect and it appears to be widespread.
The following article (which I believe is supposed to be satire, but really isn't) outlines the 5 universal laws of human stupidity, all of which we have seen demonstrated by these utterly stupid people.
The stupid, in comparison, are paragons of consistency, acting at all times with unyielding idiocy.
How many people do you know who qualify? I know a couple. I'm surprised they've survived adulthood to honest. One of them being my former brother in law, a man so stupid I'm stunned to know he still breathes.