Life is hard if you're not smart, especially these days since so many jobs are getting automated away.
The peak of these people's lives is in high school and maybe college if they're truly good at the sport. It's not like any of these guys are gonna make the NFL, you need exceptional athleticism and high intelligence to play at that level.
What's the point of this post? It's pretty much common sense that the dumb guy who plays football in high school is gonna end up like Uncle Rico from Napoleon Dynamite most of the time.