Nebraska is not a blue blood program. They have some tradition but they've been challenged since the late 90s. I don't think they competed for let alone won a Big 12 Championship since 1997 (although, they were clearly the best team in college football that season) and they've continued to be garbage since joining the B1G.
Nebraska is a tiny state in terms of population - a lot of the state outside Lincoln and Omaha play 8 man football in high school. So they have to recruit regionally or nationally. Regionally they're up against Texas, Texas A&M, Baylor, OU, Ok St, etc. Nationally, with all the $ that's poured into college football in the last 20 years, lifestyle, TV exposure and literally everything else favors schools not in the middle of nowhere with freezing cold winters and nothing to do.
Also, in today's information age, I think it's a lot harder to recruit less savory characters and fake their eligibility. And it's probably also a lot harder to keep a guy that rapes the same girl twice in a semester (Christian Peters) or a guy that beats his girlfriend, drags her by the hair down the steps and smashes her head against a mailbox (Lawrence Phillips) on your roster than it was in the Osbourne era.