Some games are close, then get out of hand in a hurry. Other games are out of hand early, but late scores make them seem closer. Wisconsin's wins over Minnesota and Michigan this season are examples of each. The Minnesota game was close into the third quarter, and didn't feel out of reach until the 4th quarter, when, at 24-10, the Badgers denied Minnesota an the goal line on 4th down, took over on downs, and marched the other way for a score on six plays, taking a 31-10 lead. Until then, Badger fans remained nervous. Minnesota connects on either of its passes on 3rd or 4th down and it's 24-17...It became a blowout in the 4th quarter, and ended a 21-point game.
Wisconsin was up 28-0 against Michigan at the half, and 35-0 late in the 3rd quarter. Two meaningless touchdowns made it a 21 point game, but it was never anything other than a blowout. The Minnesota game was much closer.
Nonetheless, 21+ is always a big score differential.