Because it's Cover 4 Man, with the Corners playing Quarters coverage.
The Safeties are covering the Double Dig Crossing patterns against Trips left formation (3 WR's to the left hash, with the Z & the Y both running Digs across the face of the Defense).
Bissainthe does a good job of picking up the underneath coverage & passing him off to the Safety, who has eyes on the QB to watch for if the WR breaks his stem or if the X throttles down for a Curl or a Comeback.
Meesh picked up his man perfectly & so did Romanas.
The only person who made a mistake on that play was Damari.
He's in Quarters playing Press Man, he's not supposed to, nor does he need Safety help. All he had to do was not spin backside towards the sideline & allow the WR to get free reign running a Post inside.
What he was supposed to do was jam & Steer him at the LOS, then flip & close the distance towards the WR's inside hip & play from his outside shoulder. If he executes proper technique like he's supposed to, it's either a PD or route stoppage incomplete pass.
The ONLY reason the WR got the catch, is because Damari turned in the wrong direction off the snap. That play was 1,000% on the player & not any Coach. There isn't a single Coach on Planet Earth that would instruct a CB to do that, literally not one.
It's the equivalent to a RB getting the hand off & then just running in the opposite direction of the LOS.
Not even a PBU or incomplete…..if Damari impedes his man’s route by .5 seconds Baron is going to clean McCords clock. Who knows maybe he gets a strip sack and we score easily from there. Ball game. The little things kill us.