When Facebook released a 13-page report in April announcing plans to combat fake news, it intentionally left out all references to Russia. According to The Wall Street Journal, the company's lawyers and policy team were afraid their understanding of Russia's actions was too speculative:
"At the time that we published the white paper we were not in a position to know for sure who was behind the activity that we described and we did not feel comfortable making a definitive attribution," Facebook said in a statement.
In November 2016, Facebook CEO Mark Zuckerberg said the idea that false information on Facebook influenced the election was "crazy," but by September, he admitted that Facebook had a responsibility to stop foreign interference in U.S. elections and help preserve democracy.
Facebook reportedly cut Russia from election meddling report (CNET)