If you were to choose someone to lead this country top on the list of priorities would be qualifications, such as education and job experience.  If we were to look through the bible we would expect God to use someone of the same stature to spread His word.  But instead He picks people that are unqualified and in the case of Moses couldn’t speak all that well.  God chooses to show His power in this way so that people will see His power working through the person and not the individual speaking.