Difficult to answer, but many times I believe it can be chalked up to blissful ignorance, a strong awareness of their weaknesses (deemed by society) and compensating therein, strong sense of self probably skewing toward narcissism, or relentless resistance to the status quo...for those who seem to be perpetually 'confident' despite their lot in life.

The word 'confidence' gets overused and distorted I believe. There seems to be unneeded emphasis on being confident all of the time, when a lack of assurance can very well lead someone to questioning themselves/thinking outside of themselves, which leads to greater knowledge overall. Basically I've come to view the intent of the word in the way most people mean it nowadays, as being synonymous with blind certitude. An attraction toward the trait even if it's completely asinine. This is particularly reinforced with men from women and other men alike, and this odd code of 'masculinity' may very well account for why you see a lot of stupid actions originating from men. But I digress. Different discussion for some other thread though I suppose.