It's true that no one wants to go to an outdoor stadium in the winter - ugh! However, there are indoor stadiums all across the country; there's even one in Atlanta. For those, the time of year is irrelevant. If they are only doing a few of these Classic shows, they can schedule around teams.
You use stadiums for sports typically unless it's a music festival or a huge name, and Azoff was billing the "Classic Northwest" as a festival, but in the end it was just two acts. Of course it's not going to fill a stadium.
Maybe they just needed a reality check. Or maybe I'm totally off-base. Who knows!