Is having had success at getting a team promoted necessarily the most important thing to look for in a manager required to resurrect a club mired in failure? I think other qualities might be more important.
Winning promotion, or failing to, can be the result of a happy coincidence of a lot of factors and not necessarily an indication that the manager has some magic formula. How many managers who have taken a club up to the premiership in the last decade or so are still managing at that level? Not that many.
And, perhaps more telling, how many have done it more than once? Off hand I can only think of Keegan in that category.