In the case of Bob Lewis, according to what he says in the interview linked above, the revival sent him back to his mother to learn a whole lot more old songs. Interestingly, again according to what he says, while he was initially uncomfortable in the folk clubs with, among other things, some git in a greatcoat criticizing the way a song was sung, his mother was quite exacting in her evaluation of his progress with songs she was teaching him.

If you haven't read the interview yet, do; it is really quite enlightening in regard to the issues being discussed here. (Thanks TheSnail!). (Although, as a git formerly in a greatcoat, I resemble that remark ... ).