UK have the WO out and the TE on the right side both go long. We had a CB on the WO and an LB on the TE, with the Safety over the top.
When the TE got so deep, the LB (who was covering his drop zone and giving run support) has to pass of coverage responsibility to the Safety. This obligated the CB to man coverage. This scenario would have been understood before the snap.
This issue is that the CB did not jam the CB well enough (see CNS' jesters to the player after the play) and the WO got behind him and continue deep.
When the LB stayed shallow, confirming the pre snap assumption that the two receivers on the right side had to be in man coverage, the QBs read is simple...which receiver is open. That was the WO, and the pass went deep and outside.
The Safety released his man coverage once the ball was in the air, but by that time the WO was give enough time to get too deep for the Safety to help with the blown coverage. Pitch, catch, run, TD.
That is how it happened. Or in other words, blown coverages happen sometimes.