At the point that the lb started his blitz, Hill was blocking the DE. He saw a clear path to the QB and took it. He could have also been thinking that the lb on the weak side would also get him if he released for a pass. The problem with that is that Davis did the same thing and did a delay release and the lb went with him, leaving nobody home to defend the TE, Hill.

The whole idea of designing plays is to force this very situation, where a defender has to pick one thing or another and then once that has happened, the offense reacts and does the opposite of what the defense "chose."

If the lb on the weak side had stayed to defend the TE, Davis would have been open up the sideline.

If the lb that should have defended the TE had just stood there while the TE blocks the DE, that would have been stupid. He's told, if the TE is blocking, you're blitzing. You'll have help from the weak side backer or a safety if the TE releases.