I think that the question needs to be asked: is the perception of a weak B1G simply due to the fact that IU is bad and NW fairly decent?
The media has its darlings snd the media shapes perception. One only has to listen to DickieV and ESPN to know that conference strength is heavily correlated with media favorite strength. Take the Big12, Kansas has won or tied for first the last 13 years. That tells me a conference overall is weak, yet the conference is perceived as strong because a media fav is strong. NW, a historically weak team, is doing well so the B1G must be bad.ACC teams can accumulate losses yet not drop in polling because the other ACC teams are strong according to perception. On the other hand, a road loss in the Big Ten is a catastrophe and cites weakness.
Branding can often allow the maintenance of a strong market position before poor product quality catches up over time. Think US autos in the 1970s and 80s.