I think there is a very simple and logical explanation for many, if not most, of Belichick's hires: he hired people he knew, and people he knew would do whatever he told them to do. Lombardi, who I think is a total clown; Kitchens; Bill's own kids, and his friends' kids. Aside from a few position coaches here or there, that's basically how our staff was created. I don't think Belichick is stupid, but he's 73 and has always been pretty obviously egotistical. It's perfectly fine to be egotistical when you're backing it up with results - for years there it really didn't seem to matter who Belichick brought in as his coordinators, as long as they were guys Belichick was comfortable with - but Belichick hasn't been doing that for several years now. So no, I don't think hiring Kitchens is some galaxy-brain move and suddenly when Clemson comes to town we're going to break out the "real" offense or something. I think Bill simply hired someone he already knew, with a preexisting connection to UNC, who would never question Bill and execute what he was asked without complaint. Maybe he also believed Kitchens would be a good OC, but I really doubt he evaluated that rigorously.
So in sum, I don't think Belichick suddenly became an idiot, but I do think the combination of his ego and his advancing age have led him to make some questionable hires that were based more on getting people who would execute his commands than getting people who would bring independent merit to the table.