Back to the 80s, any U.S. citizen was eligible for a Secret and even Top Secret clearance. How they became a citizen didn’t matter.
The FBI background check exists to determine trust and loyalty issues.
But in an age where the top people in D.C. just dump secrets onto the Internet, does it really matter?
I had a TS-SSBI clearance in the late 80’s early 90’s. The FBI (and NIS, actually IIRC) interviewed teachers, co-workers at the grocery store, and family and friends.
I was granted my clearance, however.