It’s a bit surprising that it hasn’t happened more often. If a team wins it all with a squad full of draft eligible players, it can be hard to field a quality team the following year.
But I think the biggest reason for these recent champions struggling so much in their ‘defending’ season is more because of playing in the SEC; where at least half the teams now are a legitimate threat to make it all the way to Omaha and beyond. The Tigers had a killer schedule this year having to play a Top 10 team practically every week.