Key to that at bat was Pena swinging at a marginal curve in a 1-0 count in that AB. A 2-0 count would have guaranteed at least two fastballs in the rest of the AB.
Everyone wants to be the hero. There's certainly no Marvel Superheroes called The Walker, but the pressure is always on the pitcher more than the hitter in that situation. Pena bailed him out and allowed him to throw another curve and then throw a marginal fastball strike the ump could easily call for strike 3.