Ruin Explorer
Legend
We should not equate "there was a massive increase in sales" to "there was a massive increase in people learning it from the books by themselves". All the increase shows was an increase in the player base. It does not speak directly to how they were learning.
One DM, setting up a new group, can teach a whole bunch of folks. Do that twice (once in high school, once in college, say), and you have a massive increase in the player base.
You don't need the internet for viral marketing to be effective.
So you're basically denying that the old D&D boxed sets ever got any significant number of people "into" D&D, and that the people who cite that as how they got into gaming are a meaningless minority, and that similar future efforts are worthless?