You guys are overthinking this.
1) The Big 10 West is the worst division in the history of college football having divisions. Even the old Big 12 North, at it's worst, was doing things like regularly beating Big 10 teams in non conference play. The teams Iowa plays are so fucking bad that all you have to do is not fuck up, because they're going to fuck up a bunch and literally hand you the ball in positions where your defense or special teams can score. On top of this, Iowa frequently misses the good teams from the East. When they do play them (Penn State this year for example) they get fist fucked. Michigan will fist fuck them on Saturday.
2) Iowa's defense is legitimately quite good. Not only are they almost always in the right spot, when they are gifted turnovers, they rarely drop them or fail to complete the play. They have a system, and they execute it perfectly.
3) Anyone who has watched Iowa football on a regular basis the past 15 years can attest that they have a really amazing amount of luck. If you watched on Black Friday, you'd see there were at least 3 occasions where Iowa ball carrier fumbled, and the ball bounced right to Iowa. Nebraska, on multiple occasions, committed turnovers that were not forced by the Iowa defense (but capitalized on nonetheless). There's the infamous gif of the 2 ISU punt returners running into each other to create a fumble late in a CyHawk game. Iowa did nothing to cause that, but it happened. And this shit happens to Iowa on a really frequent basis. I'm a believer in making your own luck to some extent, but I can't look at the film and tell you what Iowa is doing to make QBs throw balls directly to Iowa defensive players when no WR is anywhere close, how Iowa manages to fumble in ways that bounce the ball directly to their own players thus preventing turnovers, or make opposing players just literally run into each other and or drop balls, but it happens week in and week out and has for a long time.
TLDR Iowa plays a god awful schedule, has a very good defense, (and to the first point) is a regular beneficiary of their opponents incompetence.