Battlefield Earth, what the heck was that?

[FaxModem1]

I watched that movie, and was wondering, why do they give so little exposition on the characters, the world, the history. Nothing is really told. And the fact that one human with a little bomb can blow up an entire home planet was weird. Another thing, the assistant is helping the humans, after they pretty much destroyed his species, how stupid is that? What was the point of this book? Did it have todo with Scientology? and what is Scientology anyway?