What you're describing isn't a flaw in the research, though perhaps it is a gap. You can answer the question "Are people with dark personality traits more likel

What you're describing isn't a flaw in the research, though perhaps it is a gap. You can answer the question "Are people with dark personality traits more likely to succeed?" in the negative even if "successful people with dark personality traits learn to cover up their dark traits". Sure, in some sense the ultimate "dark" person has more options and is strictly better off (or at least not worse off) for that reason. But concomitant with being dark may be a range of other attributes which lead to unhappiness, discontentment, or lack of success.