One mistake managers can make when recruiting new staff is being too cautious and careful in their approach. Subconsciously there may be a fear of taking on a new person who could ultimately pose a threat or a challenge. It is human nature, but it is sometimes the case that managers will not want to employ an individual who could potentially challenge their position or undermine authority within the workplace.
High achievers are usually aware of their skills and talent. I have sometimes spoken to managers who are worried that someone overly ambitious and driven is going to upset the equilibrium within the workplace. They have got themselves into a position of authority and almost feel as if they have to defend it.