Early on during the resurgence of American running, I think that the internet played a big role in disseminating training information. But its impact in the last decade has gone way beyond that.
Our sport is niche. It's not on TV, and it's not in Sports Illustrated. It was easy to live in your own bubble and think that you were good because you finished 5th in your high school conference. Today, everyone involved in the sport has an easy time of knowing what's going on around the country and around the world. 9:20 ain't so hot when you see a train of guys breaking 9:00 in the big high school meets.
The internet has also made it easier to follow the pro side of the sport, and not just the races. We get youtube videos and instagram telling us what elites are doing, day in, day out. That stokes enthusiasm and makes running cooler. It also makes those pro athletes more valuable to brands, so there's a much wider range of sponsorships available.
In the post-collegiate world, the internet has been huge in keeping people involved. If you're some 2:25 marathoner in 1995, you might have a few training buddies, but you're basically living in an isolated world where you and a couple of people care about what you're doing. With the internet, you can get hundreds of Strava kudos when you run a great race, even if only a handful of people actually saw you break the tape in person. It also allows you to maintain a sense of community with former teammates scattered around the country. I think this is the primary explanation for the explosion in Trials qualifiers. People feel like they can actually get some recognition and that there's a larger group of people supporting them.