It seems to me that there is no "Folk" circuit as such.
There are so many different versions of "folk" that it is impossible to pin down exactly what we would mean by success in the folk genre because it is such a wide field and encompasses so much music and other forms. (obviously)
I have noticed that the few times I have been to concerts with big name stars, they have got the skills and talent to do what they are doing at least adequately. They also have something else which I suppose you could call charisma or presence that lifts them that little bit above all the others who maybe have similar or even better skills.
The very best ones you would want to see whatever genre they chose.