it was the dossier that instigated it. It was not until the unreliability of the dossier and the admission by Comey that it was unverified by the FBI that they suddenly completely changed the narrative to saying that it was because of Papadopoulis, even though he had never been mentioned before as a source even tangentially... and his indictment is more exculpatory than incriminatory of Trump:
http://www.nationalreview.com/article/453264/donald-trump-george-papadopoulos-indictment-exculpatory-trump