I think the underdogs are winning because this has been a FU'ed season. It's what I expected but wasn't brave enough to follow through on my pickem. Maybe it's because there is more parity, but I think it's because there was a disturbance in the force.
I believe that there are multiple factors at work in the upsets. Here are just a few factors that I think maybe have contributed to the underdogs being more successful than normal.
I definitely believe that the lack of OOC play affected seedings, which led to the BIG 10 being crowned the best conference and the BIG 12 being crowned the runner-up. These two conferences ultimately showed that those crownings were errors.
I think that there is more parity in basketball across the country. Parity is much easier to create in basketball because of the smaller sample size per team. There is still dominating teams but much less so than in the past - the talent pool is growing larger and larger I think.
Lastly, I think that the game has changed to a point where some coaches are going to have to adapt or depart. You can't compete with these 3-point juggernaut teams with an old style game plan. They are simply too explosive. Unless you catch them on a down shooting night, you better be able to put up some points.
Finally, we will likely never know the extent to which COVID played a role in the tournament. The mid- to long-term effects of the virus are just not known at this point. Athletes who contracted the virus may have been at a severe disadvantage to players who didn't.
I will say that until yesterday I was enjoying this tournament more than any in quite a few years. Almost all games before yesterday were close and the underdogs were winning more than their share. Its been exciting to watch.