The line between "elite sponsored runner" and " running influencer" will continue to blur.
Of course the difference is that Molly has an Olympic medal and is a 4-time NCAA D1 Champ. People like Matt Choi (and really anyone running around 3 hours for a marathon are a dime a dozen in the sport imo). Yet people like Matt can shotgun beers and film during the Boston Marathon and get way, way more "likes" and have a bigger following because they are more relatable to the masses or a "hybrid athlete" (or whatever that means).
But if one is active online and they have a decent social following (no matter how slow or fast they are) they have "an influence." Brands do recognize that as well as the engagement.
I don't know Molly really well at all, although I had a nice chat with her after the Honolulu Marathon (she had raced the 10km there). She seemed pretty down to Earth and was quite friendly.
In terms of social media engagement (taking the whole "Influencer" angle into account)....doing events and racing very frequently is part of the formula. For example: the Boston Marathon one week, then the London Marathon the next...then doing some promo for addidas/puma at their HQ for something. Also product/shoe reviews and filming during your race to show interaction with the crowds/fellow runners and yelling things like "Let's Go!" every mile. You get wined and dined and travel all the time as well as free product from all the major brands. And all you have to do is have that camera out recording everything on a selfie stick and posting some nice edits to social nearly every day!
Of course for a real elite/fast runner like Molly the expectations are a lot higher. You don't just jump in the Boston Marathon and then the London Marathon the next week. If takes some pretty serious focus to run a 2:20s or faster marathon (or nail an ultramarathon trail race at a high level).
Influencers really have it easier than fast pros because it doesn't really matter if they run 3:05 or 3:45....as long as they finish and get another star in the marathon majors they are seen as being an inspiration or a "hero."
In any case, I apologize for the long rant. I think for runners like Molly (especially given her sister is an "Influencer") it's easy to get pressured from social media because you feel like your career is on the line all the time. I think we'll see more very high level road marathon runners like Des Linden and Molly start doing ultras more in the future though. It is a fun niche of running and it can be a good break from pounding the pavement.
It would be great to see runners like Molly and Des mix it up on the trails/ultras more...especially if they are staying healthy and have some specific build-ups.