Without knowing the details of what happened, they did (imho) the right/ most natural thing. It all happened in a couple of seconds at low altitude (500 ft?), waiting for the damned engines to respond, going for minimum decent rate, but obviously not allowing it too stall. At the altitude it happened, in landing configuration, it probably wouldn't make sense to dive to the best glide speed. (just my opinion ofcourse) I am sure it has been replayed on the sim already many times...
If both engines go in relax mode at 4000 feet, it is obviously a different story.