What if they really were practicing those 8-10 yard cushions on short yardage, and getting good results in those practices? It's complete speculation, but it would help explain (some of) why they kept showing up even after getting burned week after week. A dash of stubbornness makes up the rest.
It would be a classic case of practice being a poor barometer, due to very superior DBs over WRs in general. Our offensive scheme+player ability was just SO divergent that it was tough to get a good read on EITHER O or D when they're practicing inside the team (also explains the popularity of combined-team practices), because the DB's were talented and athletic enough to overcome bad scheming and still make plays.
It also reminds me of the absolute dominance of the "Sack City" defense of a few years ago... IN PRACTICE... which then flopped and put up sack goose-eggs through 5 or 6 games. It wasn't a historically-explosive D line... it was an utterly hapless O line.