Quite skewed analysis if it's based search terms, given that some parameters have shifted in the last years. Google used to be a jump-off/quick navigation point to go web-sites people were very familiar with. It was convenient instead of having to type in the web-site url to just Google it, and then go. But recently, most links are clicked withint/from a social media context; thus Google is becoming less and less a jump-off/quick navigation point. I would say, the graph shows the fall of Google more than the fall of Social Networks.

The graphs show both search volume index and news reference volume.

While I think your point should be considered, I not sure if those distortions are presented in the graph. Google is still serves as the quick navigation point to get to the social networks.