Actually whilst Cloughie took them out of non-league, it was Gary Rowett who laid the foundations of their march up the leagues.
He built the squad (including losing in the League Two playoffs twice) that then went on to get back-to-back promotions.
Jimmy F then took over and didn't mess it up. Which left many to think that he might be an excellent manager. His stints at QPR and Northampton have done a lot to dispell that idea! (as well as further bolstering Rowett's rep)