I think the young founder trope persists for social reasons, not technical. The average 25 year old "understands" the internet on a very different level than the average 35 year old- simply as a consequence of having grown up around it.
I remember reading a discussion of how some technology (lets go with smart phones for lack of my memory) was going to make newer generations lives so much different. They'll be focused around them because they're so amazing and useful. What <the folks that said that> didn't really understand was that, to the younger generation, the smart phone wasn't some wonder, amazing device that can do lots of things. Rather, it just WAS.
It's like a door. If you lived before doors, they would be amazing... you'd think everyone younger than you would be amazed they have it and love it. But they don't. To them, it has always been that way, the door just IS.