One of the most important things in the advancement in any career is a person's competency. In fact, I would go as far as to say that this is the most important quality a person can have when it comes to a person's career.
Even if a person has a lot of connections and friends in high places, eventually a person's lack of competence will cause this person to lose favor with others. Other co-workers will begin to see how unreliable this person is, and begin to point this out. And if this person continues to be promoted, then people will begin to question the system. They will see the injustice of the situation, and this will cause poor morale.
In short, the bare minimum for advancement in one's career is competency. After this, it is a combination of luck and connections.
The sure road to meaningful work is the path where your interests and competencies intersect with who you are and who you can be [your potential]. ...[for] a career that's guaranteed to bring career satisfaction and personal fulfillment. (Nina Ham, Career Coach)