They play fast without turning it over much. Look at it, they have the most field goal attempts per game in the Big Ten and most free throw attempts (those 2.4 attempts more per game than Illinois, for instance, do add up, especially when they MAKE 3 more per game than we do..) and they're 10th in terms of turnovers per game (we are 1st). All four teams that turn it over less are much slower tempo and 3 of the 4 (all but Michigan) are bottom 1/3 in terms of tempo in all of college basketball.
All those ranks are out of 363 teams in D1 fwiw. In general, they are just very well balanced in each of the four offensive factors (effective field goal %, offensive rebounding, free throw-field goal attempt ratio and turnovers). And when you watch them play, it's evident, Murray is a certified bucket getter who can score on all three levels and is a go-to guy. Rebreca is a skilled forward who draws a lot of fouls and (mostly) makes them. They can bring guys in that can really help space the floor and will knock down threes if you leave them open. They don't make a lot of mistakes, and have good ball movement, so they do not waste possessions.
There is also the adjusted factor, in addition to the Big Ten gauntlet, they faced Seton Hall, TCU, and Iowa State out of conference who are all elite defensive teams, with Clemson and Duke also being good defensively. (Not to mention mighty Eastern Illinois /heavy s, they just shot like doo doo that night and weren't getting as many offensive rebounds as you'd expect for that matchup)