I don't think that Mizzou intended to play an incredibly easy schedule this season. They have run into good programs in down years - or have simply handled easily those teams that aren't in down years.
Notre Dame is coming off five seasons in which they went 120-50 (.706) in the Big East. They're only 10-6 (.625) this year. Missouri beat them by 29 on a neutral court close to home.
Cal, including this year, is 76-41 (.650) in the last 4 years under Mike Montgomery. Missouri beat them by 39 on a neutral court close to home.
Villanova has been consistently good for nearly a decade. In the last 7 years, they have gone 172-73 (.702). This year they are 7-8. Missouri beat them by 10 on a neutral court close to Nova.
Illinois is a huge rival game every year. It is always close. Illinois has been very good lately, but not elite. They've had three straight 20-win seasons and have won 20 or more in 11 of the last 12 years. They're not the six straight 25+ win teams of the early 2000s, but they're still decent and are 14-3 (their best pace since their 37 win team in 04/05. Missouri beat them by 4 on the same neutral court they use every year.
Old Dominion has won 25+ games in three straight years, going 72-26 (.735) over the past 3 seasons. At 8-8 this year, they're having their worst season since 03/04.
That's four of the top five teams they have played that are in down seasons. They can't help that since these games are sometimes scheduled 2-3 (or more) years in advance.