It means Social Media heavily influences elections. And I think Elon is saying that this interference is even worse than outright election fraud; Because you can convince people to vote for a candidate you want, and that vote will always be legal. You can convince people to riot and cause mayhem, as they did with BLM and Antifa. How does that relate to the guy in the Viking hat? Well, who's to say we are impervious to their manipulations? Who's not to say that all this evidence of voter fraud is actual evidence? What if both sides were duped?