> advised on polling statistics for the Trump campaign
Going out on a limb here, I'd guess it might have something to do with that? It would also be very foolish of them to ever admit it and I bet they will come back and say it was an innocent "algorithm" mistake if this blows up too much. Unless someone internally leaks the mechanism or the reason it would be hard to tell.
I think Google, Facebook, maybe Twitter and others are furiously working to fill the void left the failure of the traditional media to manufacture consent. Large traditional media conglomerates had one job and that was to make sure a particular presidential candidate won and they failed. Very quickly after Facebook and Google issued a statement how they are blaming "Fake News" and how they will be working on controlling and eliminating that.
While it all seems innocent and helpful "Oh look Google is working on eliminating hate and fake news, isn't that nice". It is also a signal to those who have billions to spend on campaigns (political, marketing, etc) saying "Want to manufacture some consent? Come to us, let us help you. CNN/NBC/NYT are too crusty and old and not effective anymore. Inconvenient statistics getting in your way, don't worry, they will be silenced".
As others have said it KGB or Stasi would have given everything to have access to the kinds of data Google and Facebook has. I think it is foolish to assume these companies will just use that data just to sell ads, share cat pictures and connect you with your old classmates. I think they will start selling "silencing" as a service (SaaS) at some point.