> Do you think pre-Internet mass media — one-way communication from corporation to consumer — does not propagate groupthink and shared narratives?

It certainly did, but not as quickly, and not in a separate channel from the media itself.

Put bluntly: today's journalists, entertainers, and influencers can very quickly arrive at the same (sometimes factually incorrect) narrative through following the same in-group of people on Twitter, which then results in "real" news, entertainment, and other media being produced that share the same groupthink and narrative. This can happen in hours, even minutes.

But it's not clear to your average consumer that what's dictating the stories on nightly news, Saturday Night Live, or the late night shows is actually Twitter, and the ease with which the same people can create the same bubbles without explicitly coordinating.

Size. Market penetration of Twitter is orders of magnitude above that of Nintendo or your friend. You should rather ask: how does influence scale relative to size?