With system redundancies, an airliner doesn't usually crash by reason of one glitch alone. Typically, an unfortunate confluence of them must conspire to create disaster.
Is Eberflus' scheme at fault? Yes. Are participating players at fault? Yes. (Both can be true at the same time.)
Singling out Diggs for particular criticism, it appears his wheels - and any physicality that once rode upon them - have vanished. Probably for good, following his most recent major injury. Others here have commented on what appears to be a diminution of effort since a favorite teammate was sold up the river to the frozen tundra. In any event, he's not even in the game when he's out there, and has become a glaring liability.
Eberflus allegedly knew today's opponent like the back of his hand. However, that inside knowledge was of no consequence, as the inept pass coverages employed - unfamiliar & baffling to even seasoned defensive-minded coaches like Rex Ryan - were every bit as porous and ineffective as they were against the Giants last week. If he & his scheme were any good, he'd still be with Bears, would he not?