There are two reasons for the use of the term fake news for a lie:
- Hillary used the term first, and it feels good to throw it back in her face. And,
- Fake News indicts journalism for claiming objectivity and telling whoppers. And our fondest hope is that the media has/is "jumped the shark and is losing its ability to add ten points to the Democrats vote by conning the gullible.
I don’t quite remember all of the details, but I recall that the term fake news was used to describe stories that the left reported to make the left look very bad. Then the people on the right would get get all optimistic and promote the heck out of it. Then the left would report the truth to make the right look like kooks and deflate their enthusiasm.