When you have a venue with bench seating, especially when people wear bulky cold weather clothing, it is easy to cover the empty seats when people spread out a bit. If there are 26 seats in a row and only 23 or 24 people in the row, you won't see the empty space as with the size of an empty chair back seat. It disappears as people take advantage of the extra inches of room. The maroon seats are harder to see when open although the gold ones badly stick out.
Why did people no show? It comes down to several factors together. StubHub speculators and professional scalpers got stuck with extras, people went deer hunting and didn't dispose of their seats. We have an older core of season ticket holders that doesn't like to sit outside, often deciding whether or not to attend as late as game day depending on the weather. Stuff happens in life and people couldn't make it because of work, big school projects, household chores, the kids having traveling basketball or dance class, getting the flu or whatever. There are corporate seats that get bought, stuck in a desk drawer, and forgotten about. Someone might have had four tickets, could only find two other people to come, and ate the leftover.
I noticed the odd empty seat here and there, but no large blocks of empty seats or rows as is the case when tickets go unsold. This easily was largest actual crowd the Gophers have had in years. The large crowd also once again showed that the stadium sometimes feels the strain of big crowds with longer food and restroom lines, more concourse congestion, and the failure of cellular data networks.