In terms of win probability, Iowa's win on Saturday was never really in doubt, per ESPN. Iowa began the game with a 91% win probability (because Iowa is pretty good and Illinois is... pretty not good) and while it was an ugly, back-and-forth first half, the highest Illinois' odds of winning ever got were 32%, around the time they kicked a field goal to go up 13-10 near the end of the second quarter. It was all downhill for the Illini after that.
That said, I'm not sure anyone watching Iowa through the first half really felt quite as confident in the Hawkeyes' likelihood of victory. It was not a particularly impressive half of football. The second half didn't start off much better, either, with Iowa going three and out on their first two possessions outside of halftime. But the turning point in the game for me came on the next Illini drive. It was actually a good-looking drive for the Illini -- they moved the ball 49 yards on seven plays and had a first and ten at the Iowa 22-yard line. They appeared to be on the verge of either retaking the lead or cutting Iowa's lead to one point (17-16).
And then Brandon Snyder snatched a terribly-thrown Jeff George, Jr. pass out of the air and ran it back 89 yards the other way.
That play gave Iowa its first two score lead of the game (24-13) and that was the point when it finally felt pretty okay for Iowa fans to exhale about the outcome of the game. It was a relief borne of things beyond just the specific action on the field or the points on the scoreboard; the football gods couldn't really have Iowa lose a game where Brandon Snyder makes an incredible six-month return from an ACL injury and records an 89-yard pick-six, right? That's just not how the story goes.
The pick-six didn't magically turn the game into a win for Iowa -- Illinois did put together a 10-play, 53-yard drive for a field goal right after the interception -- but it made everything feel much easier. The Iowa offense finally clicked in the second half after getting extra breathing room from the pick-six, too; they put together back-to-back touchdown drives on their next two possessions after the interception, which stretched Iowa's lead to 38-16. And that was that.