Hundreds of Phd students were in their positions. Few made such an impact.

It's not easy to be impactful, even with a good supervisor. In Krizhevsky's case, one could even argue he had a big impact, despite having Hinton as a supervisor. Alexnet was kind of built behind Hinton's back as he didn't approve of the research direction. Hinton did turn around later and recognize the importance though.