Is there really a ''key'' to success when it comes to being a published writer?

[Ben]

In today's world, with Twitter, Facebook, Amazon, etc., it's a tad bit easier for publishing houses to gauge the market to see how a particular book might do. A novel about vampires has an immensely better chance of being published than say, a manuscript titled My Life on The Prarie. And even though the latter might be leagues ahead of the vampire book as far quality, plot, and character development, even though the vampire manuscript might riddled with bad dialogue, wooden characters and laughable cliches, it's not going to matter much to the publishers.
They'll look at the vampire script and say well, look how well Twilight has done, The Vampire diaries, True Blood......there's a market for this. Let's publish it. And you know what? I think a large percentage of the writers out there who are disappointed because their work is constantly being rejected, I think they are the people who are essentially submitting My Life on The Prarie and it's like they don't get it, you know?
They don't get it that there has to be a market for your work for it to even be considered for print. Let's say the publishers had a crystal ball that told them the vampire book will sell ten million copies and the My Life On The Prarie five thousand copies. Let's say the vampire book read like it was written by a seventh grader and the Prarie book was in fact penned by a Harvard grad with a phd in literature. Which do you think will get published? Make no mistake about it, the ultimate goal is to make money. That is why a large percentage of submissions get rejected because whoever it is at X publishing house that decides to put something in print doesnt believe the work will bring them money.
Can you think of other reasons?