It also highlights how our mind's work. We "weigh up" the information available to determine the best course of action. In this case the 'good' outweighed the 'bad' in the early stages of the approach. The crew had all the indications that everything was normal - no flags, localiser and glideslope captured and autopilots engaged. In conducting the DME crosscheck the mind would more likely conclude the DME was in fact in error not the ILS. 3 positive indications to one negative.
It took the combination of the higher initial descent rate, the outside picture and DME crosscheck to bring the doubts to a level sufficient to initiate go around.
TH