In some corporate structure, you may want to avoid over performing at a job interview. Your manager wants to hire someone who is competent, but no so competent that he will replace him.

For get an older scenario, imagine you're a hunter in a tribe and there's an alpha leader. You want to be perceived as a good hunter so that you'll get a larger share of resources but not so good that you threaten his power.

It then pays to signal that you do not intend to challenge the authority. One way to do it is to have poor self-esteem, by attributing your successes to luck.