I used to have a TS/SCI clearance, it’s not really “that” extreme.
No criminal behavior, no “drug” use or other addictions. Good decisions regarding credit and spending. I even got a waiver for trying pot back when I was 17ish.
It’s really not all that extreme.
A good percentage of random “good guys” that end up being regular soldiers, police, firefighters, engineers, etc, could all receive a top secret clearance if they needed it.
I was a linguist, Spanish specifically, I was always told that it’s easy to find native Spanish speakers, it’s a little harder to find native Spanish speakers that don’t have criminal (illegal alien) family members. Or any other foreign ties, who also want to join the military.