Its just odd to cancel something in the middle of the season and not greenlight all the shows then pull the plug for next season.
Do you think westernizing the space concept was a benefit or part of the demise?
You might be surprised how many shows have been canceled without airing all of their episodes; some have had as few as a single episode air, and because the ratings are considered unacceptable, not one more episode is ever aired nor seen.
Firefly was actually lucky in that it got such an enthusiastic response from those who
did like it that FOX Home Video (who apparently have a better head for business than the FOX network suits) delivered the entire series as intended, in order and including the unaired eps. I can't really address the wisdom of not at least getting the studio or network's value out of what they paid for by airing the remaining eps, since it often seems that what they fill the now-empty space with gets even
lower ratings. And whether you want to consider it to FOX's "credit" or not, after they thoroughly sabotaged the show's ratings through pre-emptions for MLB, they then publically issued a
mea culpa in the general language of, "We may have been a bit shortsighted in frequently pre-empting a new series, still trying to find its audience, and might have had better results had we thought of this beforehand. We'll try to keep that in mind in the future." Of course, the future was already too late for
Firefly.
As to whether the Western elements may have had an effect: of course they did! If you had seen the discussions here, you'd have seen many sci-fi fans who just couldn't wrap their heads around "science fiction" that had horses instead of hovercraft (although one of the unaired eps
did have a hovercraft

) and bullets instead of blasters. To many, sci-fi is synonymous with ray guns and robots and spandex and
aliens, not a lived-in universe of human beings who, despite living on other planets and traveling twixt them in spaceships, look more like the Old West than Metropolis (Fritz Lang's, not Clark Kent's). Now, there are several very good arguments that such a situation is
more rather than
less likely under the circumstances of humanity's exodus from Earth, but they weren't explained in the course of the show - IMHO, to Joss's eternal credit, because it made the show feel more real if it wasn't bogged down by a bunch of characters explaining
to each other the things they should take for granted. In much the same way that the original
Star Trek series simply took its circumstances and technology for granted, unlike later series that explained everything with technobabble and pseudo-science in an effort to "seem" high-tech, but more accurately just seemed silly (and sillier as it went on).
And if the
sci-fi fans couldn't wrap their minds around a concept that brought back the Old West on other worlds, then non-sci-fi viewers must've suffered a one-two punch: here was a Western show - already considered a 'dead' genre -
but it had spaceships in it, too?? 
All the smart writing in the world isn't going to help when the viewer is suffering one of Sheldon Cooper's facial tic storms as he tries to figure
that one out!
Still, it's better - IMHO, again - to have a thoughtful concept, with solid characters and well-crafted storytelling, that dies prematurely than to be given nothing but the same old sitcoms and reality shows, and no effort to ever reach people on a level that rises above their necklines.