Social media are behaving like guns.
One of the major constraints on the dissemination of propaganda is its cost. It costs money to influence large numbers of people through media. The same can be said about guns; now that large numbers of firearms can be cheaply produced and marketed, and where it has become possible for large numbers of people to acquire and own them, whatever social problems they provoke become magnified.
Technology doesn't cause problems, but it does make existing problems more ubiquitous and dangerous.