The game was canceled after the Bears had a positive COVID-19 test and then a number of players isolated. That meant that they had less scholarship players available than the Pac-12 threshold, and thus could call off the game as per conference protocols.
Brady posted "More suicide deaths than coronavirus deaths the past two months. So wash your hands and wear your masks, but don't forget to be nice to people and look after yourself." Politifact rates that claim false.