I don't think it was as anecdotally rare as you might think.
I don't think the LGBT+ population per capita has changed all that much. I think people were less inclined to admit to being LGBT+ (either to others or oneself), as it wasn't as openly accepted back then as it today.
I personally knew nothing about it until I received a rather curious phone call from a classmate around around puberty. I learned what LGBT+ and phone sex was all in one day.
I meant my own anecdote. For a while if someone learned I was a lesbian (this was in the 2000’s) they would act like I was the first gay woman they’d ever met. Some of this was even in a college town.
Now people are more out, and it seems like nearly everyone knows somebody in everyday life. And I think this is a good thing. Not that peoples’ lives are defined by identity or anything, but just for the reason I said: it’s hard for society to other people when they’re concrete and real, not something “out there, somewhere”