Because it was going to be made anyway.
For my money, the entire album is pretty damn strong, start to finish, but three tracks in particular have really jumped out at me as being excellent, not only as far as Born Villain is concerned as an album but as definitive Marilyn Manson tracks: those being "Children of Cain", "The Flowers Of Evil" and the title track.
The first and third are broadly similar, relying on a progressive chord structure tied to vaguely darkwave-styled keyboard effects to move along at a steady clip. But it's "The Flowers Of Evil" that really stands out to me from the rest, containing as it does an incredible transition from a moody, strummed-guitar piece to an explosive, joyous chorus that is as moving as it is catchy. I wouldn't call the track 'happy', but it's most definitely one of the most upbeat cuts in Manson's catalogue. And for that it gets my vote.