They almost certainly picked it just for the joke.
queer.af = Queer AF = Queer as fuck!
It's like how popular the TLD of Guernsey (.gg) is with gaming websites.
I wouldn't be surprised if they didn't even realize what country code the TLD was when they registered it.
If the big bang had never occurred, queer.af would never have died.
Ergo: big bang killed queer.af.
QED