Coaching is all that matters at the college level. There is one constant to any college program. It ain't the players...Throw Purdue in the mix.
But coaching changes made the difference at many of those places.
Wisconsin was no good for decades until they got a coach that started building things (Dick Bennett) and then lucked into a second coach (Bo Ryan) who took it to the next level.
Michigan was terrible throughout the 2000s, firing a couple of coaches (Tommy Amaker, Brian Ellerbe) until they got it right with Beilein and he turned it around.
Purdue was fading fast under the legendary, but aging Gene Keady. They hired Matt Painter and they've been a contender nearly every year since.
Indiana was a national power under Knight, then faded under Davis and sanctions imposed under Sampson. Crean got em a couple of Big Ten titles.
Illinois went through Jon Groce, but found Brad Underwood.