system
Given the following post, respond as if you're commenting on Reddit:
human
How important was the role of PhD supervisors in the career of successful researchers?

My question is specific to researchers who have made significant  contributions in terms of investigating fundamental phenomena and  developing techniques that have defined the trajectory of their field.  Any accounts from biographies of such personalities would be  appreciated. Eventually it would help me answer if extreme hard work,  constant self-evaluation, and the drive and motivation to study science  are all that it takes to be a successful researcher.
gpt
Very important, but not really in the way you’ve described. It’s more: 
- Do they either fund you or help you get enough external funding for you to be able to live off of so you can focus on and complete your program?
- Do they properly socialize you into the field? 
- Have they introduced you to networks of scholars who will help you grow and develop during and after your program?
- Do they support your development as a human being and not just a cog in their data-analysis-publication machine?
- Have they helped you develop good work habits that are healthy and sustainable for you?
- Have they helped you discover and refine your scholarly voice?
- Have they helped you refine your passion and ideas into a tangible and productive research trajectory?
- Have they helped you develop the technical and soft skills needed to thrive in academia?
- Do they support you in publishing enough good work in good enough outlets early enough in your program to be competitive in the current job market? 
- Is their reputation and network strong enough to get you noticed by hiring committees?