A big part of it comes from the days when their big-name schools were in the WCHA.
Some of us really liked seeing Michigan come to Grand Forks every year. They played with an edge, the Sioux always played with an edge, and it was like smoking at a refinery. Sooner or later something was going to blow up. Epic, epic battles. One game in 1979 lasted 3 1/2 hours ... it was 9-8, there were 3-4 fights, and it went into overtime.
I liked watching Michigan State back then, but for different reasons. They were so hapless you didn't know what would happen next. In the playoffs (79 or 80, I forget), a Michigan State guy skates out to the blue line, wipes out, and knocks over the goalie and another teammate. In addition to the largest roar a visiting team ever got in GF, it was fodder for the wipeout that was yet to come. The games weren't even close.
Notre Dame was just sad. This school with all the great sports traditions, and a bunch of schmucks playing for their hockey team. Er, um, sorry Don.
Other than those 3 (plus Ohio State who never was in the WCHA), its a bunch of classic underdogs that are underresourced, underpaid, overworked. I'm happy to see any of them rise up and bite the big dogs in the butt - it just hardly ever happens.