Extensive research has been done on leadership traits. Among the traits studied and reported on this website have been IQ, personality, and emotional intelligence.
The leadership trait, intelligence is associated via research with many social advantages:
It is a leadership strength when the leader's IQ is slightly higher than the leader's followers. Slightly higher translates into about 10 IQ points. This extra bit of intelligence is one reason the leader is a leader. He or she can interpret the numbers a bit better, extrapolate from the number as to what is likely to happen, see a bit further down the road and course correct. These are all expected leadership traits.
However, when a leader's IQ is signficantly higher, both leader and follower may be frustrated with the perception that neither "gets it." When the reverse is true and the employee is significantly more intelligent than the boss, if the employee likes the boss, the employee will do their best to educate the boss. If the relationship is neutral or the employee becomes frustrated when the boss doesn't seem to care or get it, the employee will likely take their talent elsewhere.
With the current focus on the so called Emotional Intelligence, IQ has been forgotten, or worse spurned. Stories emphasizing the success of "B" students who went on to be successful business people and indeed more successful than the "A+" types who became nerds are everywhere in the leadership literature.
Those stories ignore several important points. First, "B" students are still intelligent and second the "A+" student may not need or want to found and run a business as he or she may find more satisfaction in a more specialized area such as product development, pharmaceutical research or inventing. Finally, there is no one single definition of success. Founding a business is one measure of success; it is not every measure of success.