A related note regarding Facebook here: AFAIK, Facebook's curators were very biased and were always removing anything to do support what "mainstream vocal leftists" find objectionable. e.g. Be it to do with the shameless suppression of news related to people like Geert Wilders or Pamella Geller who are not by any means right wing fanatics. Geert Wilders is a staunch supporter of homosexuals. Just because he criticizes the barbaric ideology of Islam he is labeled as a "right-wing nut" by leftists with covert/overt Islam-apologetic stances.
It is well known that Saudi kingdom has large investments in mainstream US media, that's what Trump drew people's attention to. Who knows how much of Facebook is controlled by Saudi and the likes. [1]
It's no surprise that mainstream media got the prediction about Trump wrong. I guess, there predictions and poll-results were in fact propaganda against Trump. I felt it that way, many people I know felt it and I am sure many more people must also have felt it.