Who Decides Which Themes and Sets get Made?

[Lego David]

So, I have been wondering... We already do have a lot of designers working within LEGO who are fans of original themes. This is clearly felt through the fact that we keep on getting for example Castle-related CMFs, and the occasional 18+ Adult sets. So, that means that there are at least a few designers who work at LEGO who are fans of those themes and who presumably would also wish to see those themes return as fully fledged lines of sets rather than just big expensive 18+ sets. So then, why can't those designers come together and just pitch to LEGO a reboot of those themes in a modern way? 

More importantly... Who exactly within LEGO has the power to decide which themes and sets get produced? It is clearly not the designers, otherwise we would have had Castle return as a full line of sets long ago. Is it some kind of board of executives that only care about profit and aren't actually interested in original themes? If so, how do themes such as Dreamzzz get created? I doubt that some impartial businessmen whose primary motivation is what would be the most profitable would commission the creation of such themes. And even within new original themes that we do get sometimes, such as Dreamzzz, you can clearly sense that most of the sets are trying to copy the Ninjago style and the designers don't actually have as much freedom to explore new ideas or set concepts. 

So, who actually gets to decide which sets and themes get produced, if it isn't the designers? If anyone here has had the privilege to maybe speak to some designers in person at a LEGO convention or something like that, your insight would be greatly appreciated.