Donald Trump tweeted "Some day, when things calm down, I'll tell the real story of @JoeNBC and his very insecure long-time girlfriend, @morningmika. Two clowns!" after watching MSNBC's Morning Joe. Donald Trump cannot take criticism, plain and simple. Whenever someone offers a critique of him he either threatens to sue them or come out about some "real story" about them.
People do not care about the real story regarding Morning Joe's "clowns." Donald Trump has threatened to reveal the so-called real story. However, Trump has no credibility, after fighting with the media and making disparaging remarks about a Fox News reporter. It is just the latest evidence of Trump trying to bully people that don't agree with him.
Trump is just attacking random people in order to look better at this point. Most people don't really care one way or another and he is not making himself looking good by lobbying personal attacks at other people. This kind of behavior is why he is continuing to drop in the polls.
This wasn't even on anybody's radar until Trump started yapping about it. My thought is that people don't care about this sort of stuff, but there's an entire industry built around gossip, and this story is especially "coverable" because the media gets to talk about itself. Before today I never worried about what the 'Morning Joe' hosts were up to, and I suspect that even after Trump drops his "dirt," I still won't care.