The suggestion is that the old internet wasn't a pure technical bubble: although the barrier to entry made it more technical than average, it was still fairly diverse because the alternative to passing that barrier was staying off the internet entirely. Now, getting online is easy, and there are millions of alternatives to the techy corners of the internet. So nobody who isn't specifically interested in that stuff has any motivation to join in.
OTOH, today's "technical bubble" isn't really pure technical either - technology went from being nerds-only to full mainstream popularity, and there's plenty of both technologists with other side interests, and people from other walks of life with technology as their side interest.