While the Big Ten constantly has a lot of good teams, very rarely have any of those teams been among the best in the nation and when they are, there's always a team that's a little better/hotter/luckier/had better coaching. Here's a refresher of those losses. When evaluating the talent levels, I'll be doing a shallow analysis of which teams had more NBA talent (which of course isn't the sole reason for these results), even if most of the players listed here amounted to nothing more than role players in the pros.
2002: Indiana loses to Maryland: I was too young to watch this season, but from what I've gathered Indiana as a 5 seed went on a magical run while Maryland was a 1 seed, so the better team won.
2005: North Carolina had more NBA talent, but the Illini's cohesiveness and 3-point shooting brought them back in the game. Unfortunately couldn't finish, and the refs letting Sean May be a bully didn't help matters, so we'll chalk this loss up to bad luck.
2007: Ohio State loses to Florida: While the Buckeyes had NBA talent in Marcus Conley and Greg Oden (whose body failed him in the NBA) and were an incredible team that year, they were just no match for the Noah-Horford Gators, who kept hitting big shot after big shot to keep the Buckeyes at bay. Gators were the better team.
2009: Michigan State gets drubbed by North Carolina, who had Tyler Hansbrough, Wayne Ellington, Ty Lawson, and Danny Green, all who went on to have solid NBA careers. Tar Heels obviously the better team here.
2013: Michigan loses to Louisville: This is one where you could attribute this to Louisville being hotter and inspired. This was the year Kevin Ware suffered that gruesome leg injury, and that rallied a very good Louisville team even closer together. In terms of NBA talent, Louisville had only Gorgui Dieng and a freshman Montrezl Harrell, but Michigan had Trey Burke, Glenn Robinson, and Tim Hardaway, Jr. This loss can be attributed to the hotness/inspiration factor, as well as the fact that Louisville played better team ball while Michigan relied too much on Burke in the 2nd half of the game.
2015: Wisconsin loses to Duke: This is a game that I feel Wisconsin should have won. The Blue Devils had Tyus Jones, Jahlil Okafor, Justise Winslow, and Greyson Allen, but for the most of this game it seemed Wisconsin's cohesiveness from their starting 5 was going to be enough to put them over the top. I'll attribute this loss partially to talent but more so to superior coaching from Duke.
2018: Michigan gets blasted by Villanova: The Wolverines had no shot here. Villanova had 4 of their starting 5 drafted in the NBA (Jalen Brunson, Omari Spellman, Mikal Bridges, Eric Paschall), while Michigan had...Mo Wagner. Michigan had a hot run to make it to the game, but Villanova had a Baylor-like run that year and were never seriously challenged in the tournament. The better team won.
Final tally: 4 to better talent, 2 to superior coaching, 1 to bad luck. Big Ten just hasn't had a team able to cap off a magical run the few opportunities the team has been talented enough to do so.