Sometimes no explanation is needed:

The NASA moon bombing, a component of the LCROSS mission, may also trigger conflict with known extraterrestrial civilizations on the moon as reported on the moon in witnessed statements by U.S. astronauts Buzz Aldrin and Neil Armstrong, and in witnessed statements to NSA (National Security Agency) photos and documents regarding an extraterrestrial base on the dark side of the moon.

Damned government demolition projects. Even on the moon they manage to screw up some historic settlement or another.