Infinity x this.
I don't see a credible rational for setting up this way, read a lot of comments of how he had to move on from deep block and counter football but that and this are not the only 2 options.
I think something all the top guys have about them is cunning and minds that project with a certain prescience. They might play in the now, but they also have a plan mapped out for the next season, or even the one after that, and they will systematically, silently and methodically work towards what they want with subtlety, most times and extract all that can be extracted from the personnel they have at their disposal whilst also planning for life without them, mostly unbeknownst to the players in question. If they want to get to C from A, they come up with a solid B in the interim; they don't stumble and bumble and uproot unnecessarily and they don't work against the best interests of what they have to deploy.
There is an echo chamber when it comes to Casemiro that he was a really bad signing because he fell off a cliff, but what the top managers do is cater for someone like him and his game, and even as he's in the door, are planning for his decline and his replacement, either dropping said player next to him, or rotating with him or even intensifying their search for his successor whilst using the [borrowed] time as a buffer. They don't have this player running around in systems that will utterly exacerbate their decline whilst stripping them of all the armour that made them so brilliant in the first place.
There's a theme with ten Hag that I didn't see coming, because I thought he was a brilliant strategist first and foremost and that such things would all be elementary for him. Instead, he's fostered the slowest midfield cohort in the league at the same time as stripping the midfield of its best athlete by far, and made them play the most manic football in the league. That's sabotage, as far as I am concerned. I don't know what goes through his mind to execute such ill-considered methodology, methodology even the most simple observation stated would absolutely crash and burn the moment it was announced.
Anyway, I'm not going to trudge through old ground, and actually re-engage in something I've accepted is folly, suffice it to say, the man lost his mind the moment last season concluded, and should have had the keys taken from him way, way, way back for it. He hasn't shown the nous or brilliance I expect from the calibre of manager I wish for us to have here. In fact, he's proven to be amateurish, which is a massive disappointment and lends weight to the job being too big for him.