It's not exclusively random people doing random stuff, but it also doesn't require a large, well funded, conspiracy. People see a fake poll that confirms their preferences and then proceed to propagate the message.
Also, consider who controls what propogates and what nobody sees.
Social media operators are like news (newspaper, tv news) editors, deciding what gets covered and how, and what doesn't. But they operate on a far larger scale, more powerful scale, and very few realize they do it.
