Players are way way bigger, stronger and much more athletic than they were in the glory years of Husker football. They hit even harder than they did at that time, but they don't hit with the helmet, they don't hit when the player is defenseless, there are no clotheslining or piling on or horse collaring, etc. but legitimate hits are harder than they used to be.
And athletic? Have you seen some of the catches being made by receivers?, or the speed and shiftiness of some of these big backs, including even QBs
Different kinds of athletes are playing the game now.
Add to that the rules are now designed to create more offense (TV viewers like offense) and it is quite a different game.
Even kickers and punters are better. Kickoffs routinely go into the end zones even though they have moved the sot of the kickoff back five yards from where it used to be.
Bigger stronger faster and more skilled players with more imaginative coaches.