Between Sunday and Monday, Michigan fell from #1 to #3, even though they last played on Friday, and beat Michigan State on the road by 12 points. (Duke moved up from #2 to #1, while Arizona rose from #3 to #2.)
So what happened on Sunday? Well, Nebraska lost to Illinois, and subsequently fell 3 spots today, from #7 to #10. Michigan just beat Nebraska last week, and has yet to play Illinois.
I'm not sure why a Nebraska loss would affect Michigan that much, but I don't see another easy explanation. Their NET breakdown (8-0 in Quad 1, 7-1 in Quad 2, 4-0 in Quad 3, 1-0 in Quad 4) did not change from yesterday to today.
Ultimately, the main thing this seems to be telling us that the differences between the top 3 teams are minuscule, and subject to daily changes. Here are the NET rankings for the last 4 mornings.
Friday: #1 Arizona, #2 Duke, #3 Michigan
Saturday: #1 Arizona, #2 Michigan, #3 Duke
Sunday: #1 Michigan, #2 Duke, #3 Arizona
Monday: #1 Duke, #2 Arizona, #3 Michigan