The title is incorrect. The correct title is that there is a stronger correlation between (CS50,Hollywood) than there is for (CS50,Nasdaq).
You could probably find that the price of a crate of lemons in Mexico for delivery in 2 months is more highly correlated with CS50 than either one of those but that doesn't mean that they have anything to do with each other.
I was part of the Malan spike (took CS50 in 2007, TF'd in 2008). Switching the first week from ANT to Scratch was a pretty brilliant move on Malan's part, along with touching on web programming in the final week of the course. CS50 was one of the top two classes I took in college, without a doubt.
I don't find this surprising. Enrollment is expected to be a lagging indicator. Effects of any "trends" may take a couple of years+ to propagate themselves between industries. If tech firms are incredibly hot today, CS50 enrollment isn't going to suddenly increase today.
This works for declines too. People continue to enroll to study finance or law in promise of riches[1] after each respective bubble has already popped.
More importantly, though, not every college freshman/high school student meticulously follows HackerNews or the latest fads. Not everyone even follows NASDAQ or can analyze the tech sector. People like "sure" things. Hate it or love it, the mainstream media and Hollywood have quite a lot to do with what people know and think.
I was one of the students on the far left of that chart - the early 90s spike. I don't recall any external influence like The Social Network, but the course had a great reputation, and the world was going through a tech shift (students had just gotten email for example). Perhaps who's teaching is a driver as well.
Who was teaching back then? Check out the paper I referenced (from the prof teaching now) - good insight onto the changes he's made and how they've impacted the class. Still, though, that huge jump at the end has to come from the outside. Ec10 was the only class larger this year.
Margo Seltzer taught CS50 for much of the 90s -- at least '95, '97, and '98 and also, I believe, for a couple years prior to that. (She was on leave in 1996, and Brian Kernighan taught the course.)
You could probably find that the price of a crate of lemons in Mexico for delivery in 2 months is more highly correlated with CS50 than either one of those but that doesn't mean that they have anything to do with each other.