Having ordered and seen the consequence of an evacuation many years ago I think this crew made a sound decision not to put their passengers at additional risk. In the case I was involved with there was smoke and fumes and so we had to assume a fire, therefore the choice was easy. However the aftermath was a real eye opener! Thankfully there were no major injuries (very lucky), but there were grown men crying people in shock etc and scattered everywhere, do not underestimate the risks of a full evacuation.
As to the reason for the incident in the first place let the authorities carry out their investigation. I am sure this crew are under enough stress at the moment re living the incident and questioning themselves (If only I had...etc). Judgements from armchair critics who do not know the full facts will not help further the interests of flight safety.