dirtyd,
Laziness, coupled with poor safety management skills, lack of SMS training, analysis and risk assessment are the reasons why..
There may be underlying factors. Was the crew on board occupying the control seats qualified to be there, for example a type rated pilot, aircraft engineer certified for engine runs in no flight crew member present. Was the pre-flight, pre-start checklist completed. Braking pressure checked, emergency braking system armed and checked?
Photo's suggest there was a tow bar attached at the time of the incident, so there would have been adequate equipment available to position the aircraft to a more sensible location.
No doubt the Underwriters will be looking very closely at all the factors.