I have this theory about Illinois and fouls:
Illinois plays a very "hands-off" style of defense. They don't want to force turnovers because they want to avoid fouls. Other teams are more physical. They're touching Illinois on defense in a way Illinois is not touching them on defense. So when Illinois starts to get a little more physical—matching how the other team has already been playing all game—the refs see that and start calling those fouls on Illinois, while continuing to not call them on the opposition, because it's how they've already been playing. Nothing has changed.
I hope I explained that sufficiently. I don't know that it's true. It's just an idea I have.