The graph depicts a cumulative meta-analysis: each new study is being absorbed into a summation of the evidence so far. With 4 studies, it's shifted from the "this helps" side of the ledger over to the "this harms" side. See more about cumulative analyses in this classic article.
"Promising" is a media and marketing staple, too. Several wonderful initiatives keep the media to account on this, story by story: Behind the Headlines, Germany's Median-Doktor.de, Japan's Media Doctor, and the US Health News Review.