TF kid and long-distance hiker here. Personally, I'm autistic and can't really function in a normal job, so spending as much time as possible in nature is the move. Funny, I always felt like an outcast even among thru-hikers anyway.
Why does hiking attract so many trust fund kids?
OP's not entirely wrong, there's definitely some of us out there. My take? There's a type of young dude - loner, dropout, no real skills - who just wants to fuck off from society. But they're definitely not the majority of hikers, at least from my experience. The trail attracts all sorts (this is just my random categorization, but you get the picture):
The finance bro doing a 180 career change.
The vanlife couple with two dogs, working sporadically.
The 19yo clearly having a psychotic break.
The 30-something ex-athlete whose promising career ended early due to injury.
Hordes of Boomers in groups enjoying retirement.
That barefoot, possibly homeless philosopher dude (could be 22, could be 53) lost in his own world/concepts.
Plus the more "normal" types: scouts, trail runners, climbers, weekend warriors.
As for why TF kids hike? Honestly, I think there are just a lot of us everywhere now, especially with this economy. Maybe the ones who haven't been completely lobotomized by the internet decide to actually go outside instead.