CU fans have been aiming at the Nebraska game for decades now. It's the Cornhuskers who've refused to buy in. CU fans have long had the necessary hatred for Nebraska, and the game means more to most Buffs fans than any other on the schedule.
Probably has something to do with the 46-18-2 all time record we hold over them. Not to offend the CU fans, but their view of the NU/CU rivalry is about the same as Raider fan's views of the Shanahan era Broncos.
With the exceptions of a few big games, CU has pretty much been a doormat for NU. They haven't really been competitive enough with us to get viewed as a true rivalry. As the article mentions, since the Big 8 became the Big 12 CU has pretty much become our rival by default.
Again that isn't meant to offend the CU fans, just my honest opinion of this rivalry situation.