The coaches are all ex players in jobs for life
We keep sacking the manager but the structure of the club remains the same, so every manager comes in has a little bright spark and then ends up in the shit.
Benitez has made mistakes, all managers do. But Ancelotti was no better just took a little longer before it went bad, Silva no better, Koeman no better
Maybe they are all shit managers
Or maybe the structure needs to change for there to be any hope of consistency