If you have a Facebook page with some level of following, with or without a website attached, there are a lot of ways to make money. Frankly, it’s easier to start with a Facebook page and build a monetized site than it is to start a site and try to build a Facebook following from it.
There are people out there who grow Facebook pages for the sake of having them. I’ve seen dozens that center themselves around a concept and grow into something larger. For example, the “I Feaking Love Science” page started out just growing a page around cool science facts and developments around the world. Over time it grew and grew, to its current nearly 25 million followers, and it has since expanded into an entire website of its own. It didn’t start with the website and grow the social pages as so many people do these days.