When they lowered the scholarship level and NU decided it needed to be a finesse passing team instead of being a power football team.
Not sure when the wheels fell off the wagon. Was it the Callahan years that stole their desire? Pelini and his antics? Eichorst? Not the same NU program I grew up with in the 80's and the 90's, for sure.
I think it goes all the way back to that short guy that Osborne named as his successor. Recruiting died and never returned, except for a sprinkling of JC transfers Callahan grabbed out of desperation.