Doesn't always work. Neil Aspin had a good record with non- league clubs Harrogate, Halifax and Gateshead. Port Vale took a punt on him and they languish near the foot of League Two.
I've looked at the promotion spots in League One and League Two.
Wigan and Blackburn both have managers with failure on their CV.
Accrington top League Two with a manager with failure on his CV. Whilst Luton and Wycombe both have managers in their first managerial role.
I'm surprised the non league route is so in favour right now.