Yahoo irrationally overpays for tons of stuff, AOL irrationally overpaid for Bebo, there was that high school girl that made a social network and makes millions of dollars so she bought her mom a house, there are plenty of other data points I filed away in my head over the years.
Tons of things happen in Silicon Valley everyday that makes no sense to outsiders, or sometimes even to those stuck in the tunnel. Are you new here? Sit, enjoy a cup of tea meanwhile.
Throw on top of that the youth obsession in tech has been around since I was 17 eleven years ago and it will continue to stay. Youth is forever a distraction that you have to grow out of. If you don't then consider seeking a therapist.
Your brain hurts from trying to neatly organize this particular liquidity event as fair? Maybe you can't. Maybe it doesn't matter. Get over it, stop the hating, and get back to work.
Funny enough, mainstream media with old talking heads are spinning this narrative two ways: 1) the ever louder need to get every child to learn to code and 2) it's so fun bit of escapism to think what you would have done with big money when you're still a teenager contrasted against the $325MM Powerball win in New York.
All in all, this barely registers as a blip on the average American considering real shit that's ongoing with fairness over marriage equality in SCOTUS.