Answer:
Where there is no diversity, there is no need for synergy. There is no advantage of one over another and there is a common flaw in everyone. Everyone sees things the same way.
Where there is diversity, however, there is a social pool of various perspectives, varying talents and competencies.
For example, it is easier to form a band where there are different people who can play different types of instruments and different people who can sing different parts.
It's exactly the same way in other fields. Variances and diversity foster innovation and creativity.
Cheers!