There is an interesting take about Fergie’s longevity that ascribes it to how much he delegated the day to day to his number 2 and then cycled through those guys every 4 -5 years. Off the top of my head he had Kidd, McClaren, Smith, Queroz and Phelan, each of whom would bring in different playing and training ideas, create a different vibe and overall keep things just fresh enough despite the consistency of Fergie’s overall stewardship.
In contrast Pep absolutely dominates every club he’s at, even at the day to day level. That has to limit his ability to keep any single project going, both in terms of the response he gets but also in terms of his ability to keep up the intensity.