Football is grueling. They're putting in hours and hours of work doing film study, weight room, and practice....on top of that they've got school to juggle. 10 weeks into the season all those hours just build up and it can be incredibly hard to keep grinding as hard as possible day after day after day. You can try as hard as you can but it's still difficult.
I get why a bunch of fat dudes on a message board are outraged at a team "losing focus", but in reality 10 weeks into an absolute grind of a season, it's pretty understandable to get worn down. There's a reason why even good teams struggle to stay undefeated, no matter how much they try to stay focused