If you took BYU's preseason predictions from Ford, he had BYU with the following likelihood of winning

• 75% vs SIU
• 15% vs SMU
• 57% vs Wyoming

So that adds up to 1.47 expected wins and a 6.4% chance (based on preseason and assuming independent results) of being 3-0

Meanwhile UNLV had the following odds

• 44% vs Houston
• 99% vs Utah Tech
• 12% vs Kansas

Which adds up to 1.55 expected wins (more than BYU) but (with same caveats as above) only a 5.2% chance of being 3-0.  It's just that UNLV had a guaranteed win, whereas BYU did not.

Same story with NIU

• 99% vs Western Illinois
• 2% vs Notre Dame
• 71% vs Buffalo

Means 1.62 expected wins (more than either BYU or UNLV), but a miniscule 1.4% chance of being undefeated

Bottom line - we excel here by having more toss-up games instead of a mix of expected easy wins and unexpected upset victories