I have the impression that, actually, this is the guy who calls the shots - not Agnelli. At the very least, he is the one who filters the options Agnelli gets to choose. No decision is made without his pre approval.
All understandable, after Agnelli burned money from the owners, coupled with complete faillure in the sportive field.
So this is the process I imagine: Allegri talks to Cherubini and Nedved. The 03 of them discuss actions needed, signings, squad management etc. When the decisions involve financial impact, they present options to Arrivabene, who sets the financial limits. After validation from him, alternatives are presented to Agnelli.
Agnelli won't ever be able to decide by himself - he'll always be trimmed by Arrivabene.
Problem is, Arrivabene is clearly is out of his depths. He doesn't understand shit about football. He gathers information from Cherubini and Nedved, and will always tend to discard more expensive options, in a superficial analysis - and by doing so, maybe setting up for more financial damage in the future, because of sportive decay.
Also, there is absolutely no evidence that Cherubini and Nedved have a clue about managing a team.
So that's where Juventus is at. A complete mess. The fact no one really knows what the roles are, you can just imply it's a fucking mess. There's no evidence any of these 5 guys has the adequate ability to decide.
And I'm sure Allegri, after winning 5 scudettos, is obviously a very important voice in the decision making process. So he's to blame along with all these guys.
All in all, Agnelli overruled Marotta - who was the specialist - and sacked him for divergent positions. It backfired like hell. Elkann lost trust in his decision making - as he should - and established a babysitter who will pre validate the options, with Agnelli absolutely forbiddent to overrule the babysitter. That's where we're at. Clear disfuctionality imo.