To me, it's an example of poorly designed plays at least as much as bad AI playcalling (why blitz a 2nd & 59?)
No defense would use this play, unless they were all but certain it was a run, imo. Otherwise, why would they leave someone totally uncovered by design, especially someone who could go for big yards? I could see if there was no one on the HB or something - but not downfield threat like a TE.
Blown coverages are one thing - route combinations/rubs are another, but just not accounting for an eligible receiver in a pass defense?
Either bad play design, or bad understanding of packages - but even a 3-4 base can cover 4 receivers in man even if blitzing all the LBs (2 CB, 2 Ss), so unless they were calling that play against a 4 WR + TE or 5-wide set, the main receivers (WR and TE) should still be covered. The HB/FB being open - I can see that, especially on such a down and distance.