I only meant in the sense that it is private organizations doing whatever they can to increase their bottom line.
I don't disagree that Facebook pretends to be an open, user-driven platform; at the same time, conventional news agencies also pretend to be open and unbiased.
As for why, I think a little of both played a part but would place more emphasis on the former.
I also think the reason was a bit of both. The editors and writers who were producing content that facebook didn't suppress probably cared about the special chance to proselytize, but people running facebook are probably doing these types of things mainly for the profits.