Watch it again.
Illinois almost never faked a blitz, regularly sent pressure, tried to stunt the DL, and played soft coverage the entire game.
It's kind of an oversimplification. I wouldn't make it into a negative. With Barkley healthy, with Hack apparently healthy with decent mobility, with an OL holding together pretty well -- all of a sudden PSU becomes kind of difficult to defend.
Maryland played the high risk D and almost came away with a win. Illinois had more confidence in their front so they played a more straight up defense. That might have been the right choice for them. The bottom line is the Illinois secondary couldn't cover the PSU receivers -- so continual all-out blitz (what Maryland did) wouldn't necessarily have worked out any better for them.
I do think it's fair to say that Illinois was playing away from home, they had played a physical game the week before vs Wisconsin. So they may have come in tired, and definitely got worn down in the 2nd half esp. when their offense couldn't sustain drives.
Northwestern will have fresher legs, but I'm not sure the NW defensive personnel is any better than Illinois.