One, I believe the design is to isolate Ford. Donny curls short to keep a defender with him. Isaiah crosses the field deep to hold the safety (two receivers on that side, both deep, only Ford on this side, safety has to honor two over one). It's a paint-yourself-in-a-corner play call (if they blitz, the quick pass is probably Donny because CW and IW are just decoying), but the whole design, in my view, is to get Ford isolated without safety help.
Two, if you're going to put this at Petersen's feet, it must be acknowledged that it worked as designed. The safety stayed with two deeps on his left and Ford beat his guy. If Julian Pearl holds his block, this is the winning TD. I might question a play call that requires this offensive line to provide a 3.5-4.0 second pocket (Peters had to release at 2.75 because of the pass rush), but this is a guard blocking a DT. No college DT should get a 2.75-second QBH.
I looked it up. PFF has this as one of only two Damarjhe Lewis QBH's in 55 pass rush snaps this season. 53 out of 55 times he's neutralized. One of the two QBH's wins a game.