1. The invention of the fake news Pence story had two purposes. A. to feed leftist 25th Amendment coup fantasies and B. to cause internal strife in the White House.
Once the media planted its fake news story, it could then...
2. Report on the reaction and run pieces discussing the denials. This gets more mileage out of the original fake news piece. While the denials make it seem as if the story has legs.
3. The final phase of media trolling is encapsulated in this LA Times headline. "Pence's sensitivity to talk of 2020 speaks to White House insecurity". You reacted to our lies. Clearly you must be sensitive.
It's childish and yet it encapsulates the cheap trolling and the agendas behind it.