At my work, we meet astronauts fairly often (I met Jonny Kim last year), and it's amazing how many of them are like this. They'll usually pass out their headshots that have their bio on the back, and the number of advanced degrees and impressive accomplishments is jaw dropping. Like I feel like I'd think my life was worthwhile if I did one of those things by the end of it, and a lot of the astronauts are hardly more than half my age. And to really rub it in, they all seem incredibly genuine, personable, and well adjusted.
There are a giant number of people who want to be astronauts, and NASA only needs a small number in a given year, so they can pick the very cream of the crop.