They weren't a juggernaut before the injuries either.
They played a lot of scrubs like the colts, bears, titans and jags.
They gave up a avg of 22 points for the year, 32 for the last 2 months if the season.
If you just look at their schedule, any reasonable offense they ran into they got destroyed on defense.
They gave up a avg of 12.2 points to the Cardinals, Titans, Jags, Colts, Cowboys and the Bears times 2.
So the injuries do matter as to why their PPG skyrocketed over the last two months. But also their pre injury defense was really low because they did their job against the scum of the league.
I guess what I'm trying to say is, I don't think the Lions defense was anything special. Injury or not.