and why these Skiffy idiots have green-lit Caprica?
They're obviously making money out of nuBSG and hope the same will be true for Caprica.
That's the only reason any company will greenlight anything and it's the way any company works. It's basic economics, really.
A strong emphasis in this strategy seems to be on the DVDs. Think about "Razor" or the "Plan" as well as the fact that the "Caprica" pilot debuts on DVD.