Why its big gain in streaming (when the song's official video premiered on Aug. 18, the day that it was released)? Swift posted four clips on her Vevo channel (on YouTube) in the past four days featuring outtakes from the video; as they include the song's audio, their clicks count toward the track's total streaming in the chart's tracking week.
The shameless chart manipulation
They need to remove video streams from the Hot 100 asap.