The examples of great teams with average classes are few and far between. Off the top of my head, Tom Osborne's Nebraska teams of the 90's weren't highly ranked, but they were great clubs.
. Nebraska HS played 7 or 8 man football and there don't get many ranked players out of that.That was when one could stockpile redshirts and build them up They would get gangly linemen bulk them up and dominate as Jrs & Srs. He also got his skill players out of New Jersey.
How about Boise recently, and even TCU to an extent? Boise at one point had 0 players that were once 4 or 5 star recruits when they were in the midst of one of their 1-loss seasons. Peterson can coach.
Nebraska is not a populous state. The schools are rural and small and they do not have a significant black population. So Nebraska has always recruited heavily neighboring states and in urban areas (like New Jersey) that produce many athletes but have few division I schools in-state. Nebraska's walk-on program is the envy of the football world and has been so for 40 years. They take a lot of corn-fed farm boys, introduce them to conditioning and training and thun them into athletes that can compete for scholarships in their junior and senior years.