Delegation does not have to be because of a lack of knowledge. In fact, it seems like if one delegates for this reason its probably a sign of trouble to come. We delegate because of lack of time.

I guess its impossible for an executive to know ALL the details of the work they delegate, but I'd be willing to wager that executives who understand the details function better in the long run.

It certainly isn't tautological that executives be imbeciles about the businesses they run.