One bad apple spoils the bunch. That is what happened in baseball. A select few teams and players have not taken signs and symptoms seriously and let players play regardless of test results. The Marlins has 2 players this past Friday test positive with no symptoms and let them play anyway. (Completely against the rules) and by Sunday half their team was infected.
The majority of the league seems to be following protocol and has not had any outbreaks. Same goes for the NBA.
The knock on the NFL has been they have not be proactive and have not really shown a detailed plan of how the season is going to play out like the rest of the major sports leagues have. For being the wealthiest league it’s a bad look.