Why is this hard to understand? The same technology can be used for both good and bad.
Obama used it to inform people about his polcies and get the out to vote. Trump used it to spread lies, falsehoods and half-truths. Essentially any media that was outlandish enough to become viral was promoted and promoted to hapless people who probably might have wondered why they were seeing so many distressing articles about America in "Carnage" (as Trump puts it).