From Daring Fireballs John Gruber:
It’s the same reason why Facebook, Twitter, and YouTube are overrun with state-backed troll accounts from Russia. Engagement leads to growth, growth is all that matters, and if the trolls and fake news are engaging, better not to look for them. The oft-quoted Upton Sinclair quote fits perfectly: “It is difficult to get a man to understand something, when his salary depends upon his not understanding it.”
Source: Why Can Everyone Spot Fake News But The Tech Companies?