Research shows that when bad leaders take a leadership self-assessment test they score themselves highly. They have blind spots about their own leadership and can’t see that they can be any better. That blind spot is self-reinforcing: it's a major reason they are bad leaders.

Yet, when good leaders take leadership self-assessments, they often score themselves lower than the bad leaders. That’s because they always want to be better, and can see a long improvement road ahead.

In other words, a lot of bad leaders are at stage 1 of these four stages of learning:

i. Unconscious Incompetence
ii. Conscious Incompetence
iii. Conscious Competence
iv. Unconscious Competence (Mastery)

Source: The four stages of learning come from Joseph O’Connor’s book Introducing NLP (Neuro Linguistic Programming). I'm not a fan of most practitioners of NLP, who see it as a way of influencing other people. But, some of the thinking behind it is interesting.