I don't think anyone implied that Facebook et al. tried in earnest to sway the election. Facebook execs endorsed candidates and donated money to campaigns or PACs but that's the routine for any company that has a stake in politics. If Facebook wanted to, they could invisibly change the content recommendation algorithm on facebook dot com to only show negative news about the wrong candidate (or 90% negative) and only show positive news about the right candidate. They could have also made up excuses to ban right or left wing figures from facebook dot com. Stuff like that is possible to accomplish and get away with, but Zuckerberg was merciful to us this time.