AOL may have put more normie nerds on the Internet, but they were still nerds. 34 million is a minority chunk of the American populace. Yes social media did exist well before Facebook in the other Giants that we all know and hate today, but adoption was far from universal. The majority of people in America did not have any sort of online footprint except maybe for email. That changed with the smartphone, between 2007 and 2012 the adoption of personal computers that follow people around ramped up to the point where by the time you get to 2013 or 2014, almost everyone in the entire United States had an online footprint. That mass adoption changed the internet from being a niche thing, even a normie niche thing, to a ubiquitous thing that everyone was a part of whether they liked it or not.

As for the uptick, look closer: It starts just before 2009. this would have been a year and a half to two years after the iPhone with its very normie friendly interface released. back then, a year and a half was plenty of time for adoption to incubate from the early adopters to the mass market