I was going to post something similar. Thinking about it though, there was no announcement made of Simon being appointed. I think members of the old DET forum got wind of it and a journalist asked Nigel and he confirmed it. I seem to remember him saying that he and Simon learned their footballing philosophy from their Dad, so shared almost identical ideas of what football was supposed to be like. Consequently, Simon was more likely than anyone to find the players that fitted with whet Nigel was trying to build.
From that it follows that the previous chief scout must have either left or been demoted, and that Nigel didn't share his views on players/tactics etc. If that scout was producing reports that Nigel thought were rubbish, why wouldn't he ignore them?
Going back to the OP, I don't think that there is a single formula for successfully managing a club. In absolute terms, Nigel, Rowett and McClaren have all failed using a variety of methodological approaches. Clement employed an army of analysts - who knows if he would have achieved promotion if he'd have not been sacked. His subsequent performances would indicate not. I suspect that Jody Morris is the technical guy now, and I doubt he'd have been allowed to coach the kids at Chelsea without using the most modern analytical methods - but we're not in the top 2...yet. Maybe this will work, and great. But if it doesn't and our next manager doesn't bother with analysts and opposition scouting, but gets us up as Champions - will any of us care?
What I'm trying to say is that it is pointless judging a single aspect of management. You can only judge on results, but that has to be contextualised with where the club was when they took over, how long in tenure and resources available.