I think the term caught on because it was a more efficient way to convey the idea. The things originally identified as “Fake News” don’t “look” like propaganda in any obvious way. They look like news articles, because they’re designed to pass as legitimate news.
Of course, the term was quickly co-opted as a way to say “this news organization has facts which are inconvenient to my worldview,” and so its meaning is rapidly becoming diluted, if it isn’t already… Which is a bit scary, considering how eagerly people seem to be taking up that mantle.
I think @MrGrimm888‘s point about invalidating media and dictatorships is important.
Maybe using “propaganda” instead of “fake news” could separate the actual idea from what has become a campaign to invalidate certain media outlets? Breathe new life into the original issue? I don’t know.
I know that US agencies refer to the issue as “disinformation.”