The Dunning-Kruger Effect, Or, Anti-Imposter Syndrome

The Dunning-Kruger effect, named after David Dunning and Justin Kruger of Cornell University, occurs where people fail to adequately assess their level of competence — or specifically, their incompetence — at a task and thus consider themselves much more competent than everyone else. This lack of awareness is attributed to their lower level of competence robbing them of the ability to critically analyse their performance, leading to a significant overestimate of themselves.

In simple words it's "people who are too stupid to know how stupid they are".
The inverse also applies: competent people tend to underestimate their ability compared to others; this is known as impostor syndrome.

If you have no doubts whatsoever about your competence, you could just be that damn good. On the other hand...