There are several factors that killed the Huskers. Number one was leaving the conference, cutting their ties to most Texas recruits. But a close 2nd was when the NCAA put limits on the number of players you could have at practice. For a couple of decades, high school players, primarily from Nebraska walked on in Lincoln with little hope of ever playing. But they were being loyal to the state school. The Huskers had much higher practice player numbers, which allowed them to put together so many scout team players, that their top 80 players didn't have to be on a scout team. Some were, but many weren't. They could have guys who only worked on the other teams' stuff.
It allowed their guys who were going to play on Saturday to focus totally on their game prep. And they could alternate scout team players to provide many more reps each week for their game prep than you can get with typical numbers. But the NCAA put the kibosh on it a couple of decades ago. Put everybody on a total limit of shipped players and walk ons. Something in the low hundreds. They lost an advantage they'd had since the scholarship limits kicked in, during the mid 70's.
I'm told that with COVID, it went back up to 125, though.