So the first ever collapse of a skyscraper by fire happens three times in one day, hasn't happened since... that's rational. A group of students takes over several planes with only desktop weaponry, and we take a third party's word on that... rational. The entire air force is like the Keystone cops when they are most needed... rational. Screw the evidence, lets get that steel to the recyclers right away to make room... totally rational.
So , away from 9-11 and back to real life, if the cops find a dead body they cremate it right away, no need to investigate, it isn't gonna bring the victim back to life... duh!