This is not rocket science. If you have invested massive amounts of money in a project and you get little reward, then you need to do something. You have tried to change managers, but have had little effect from it. Then you need to look at other parts of your business.
In recent seasons, we have struggled a lot with injuries, which is perhaps not surprising when you have a medical chief who mostly spends his time with pseudoscience, and is otherwise concerned with being a best friend with the players. You have a DOF which is responsible for the logistics of players, but which fails to strengthen the team in the position you need reinforcements, and invests in mediocre, often injured and expensive players.
Of course, these have to find something else to do. This does not mean that Benitez is protected, but it does mean that the decision makers believe that these may be probable explanations for the poor results, and they will first try this method before changing manager. If the bad results continue, Benitez will of course disappear, but he has been given a little extra time.