As another commenter said, the film was trying to make the opposite point: that Irons’ character knew full well — probably better than the other characters — what was going on.
But the detachment you mention can / is very important. When you’re working deep in the woods you really can’t see the forest for the trees. You may be working on a feature that will make the user’s life a lot easier, but the real customer is IT and your feature could be cut because the customer won’t like it (“this will add retraining cost”). In Margin Call, perhaps the thing that could increase your bonus is, from the overall company’s PoV a distraction because it’s more urgent to save the company (so bonuses can be paid out at all).
So a good manager operates at a higher level of abstraction. The best ones have a lot of experience so can see from the signals they get what’s happening at the lower levels of abstraction. Irons’ character is supposed to be one of those.
Of course the high level abstraction, when the boss fell upwards and doesn’t have the Fingerspitzengefühl to be able to see what’s below the surface, is a common problem. It can kill a company: look at how Welch and Immelt destroyed GE.
A good sign of this is also called out by a different commenter: opaque language is often used to try to cover up ignorance.