Hard to say, because the other thing that happened was that the design was refined to have strengths that none of the competitors were able to match.  The Nano was light, sleek, and nearly seamless, it had a bright, clear, colorful screen, it had superior sound, and an interface that is a pleasure to use.  By that point, all the competition had was more disk space, a changeable battery, and maybe some other minor features that nobody really cares about.