The Dunning-Kruger effect, most likely. They don't understand the thing, at all, so they don't understand they're bad at it.Yes, it's kind of like when you meet someone who is really kind, caring, and sweet...and they think they are the worst person possible.
Then you meet the biggest A-hole in the world, and somehow THEY think the world of themselves.
Never understood that. Why do people who are the worst at something (writing, being a human being) think so highly of themselves?