2 or 3 other callsigns chipped in on frequency (I'm sure they were trying to be helpful) during the emergency which, unless you are giving a MAYDAY RELAY call, goes against the idea of keeping the frequency completely clear except for the controller and the aircraft in distress.
The controller has to ask if the aircraft has a further emergency (how many do you need!!?) because he didn't go to full mental arousal prompted by a MAYDAY call?
I will reiterate that the crew did a great job landing the aircraft safely - BUT, they were descending quickly, having to pick a field to crash land into, and still being asked questions by ATC which the simple use of a MAYDAY call would likely have pre-empted.
Anyone coming onto the frequency not having heard the initial declaration of emergency would not have known there was anything going wrong and could easily have blocked transmissions unintentionally - prefixing the aircraft CS with MAYDAY each time, prevents that happening.