Was facebook the only influence in those people to vote? I understand there was a study behind it, but what would have happened if facebook didn't display the m

Was facebook the only influence in those people to vote? I understand there was a study behind it, but what would have happened if facebook didn't display the message. Here is an example, I worked on a website where we redesigned a page. All of the sudden we got an increase in traffic. I insisted that the reason for the traffic increase had nothing to do with the redesign. More page views could have been a result of another website linking to us. (the real reason was the website appeared on TV) But at the time the business team did not know that, so they just said it's the redesign. My point is, there are lots of factors that can influence the vote, and with the very little detail it is hard to say that Facebook was the cause.