This ^
Mac literally ran into the sack, if he stays put and makes the throw there is no sack.
It's not unlike the 3rd and short where he has Rhamondre is in the flat to the left, if he throws to him immediately it's a TD or at least a long gain, but definitely a first down... instead Mac waits to get gobbled up, throws a granny underhand free throw to Rhamondre too late for an incompletion. The next thing you know Obie is on the sidelines screaming in his ear see the showing him the tablet.
Most of Mac's sacks are the result of his pizz poor pocket awareness and putting his linemen at a disadvantage by moving and dislodging their leverage on the guys they're blocking. Mac sucks.