I thought more about this and I just don't get it at all. If the intention was to have a form of communication that could be used to speak openly but hide that you were gay, how did that even work in practice?
As soon as you hear someone use a word you know is used by gay people, you know they're gay, it's not like you have to know what the word actually means.
More than just the queer culture spoke it it became adopted by them for only about 15 years or so it seems. At least as a secret sort of code.
I imagine London has a lot more of a hodgepodge of languages being spoken at any one time. That combined with the thick accents and dialects of the UK would make it easy to miss at first.
I assume it wasn't freely given and more picked up through association, making it more difficult for outsiders to pick up.
The queen culture adopting it was simply the last incarnation of it after centuries of usage by carnies and showmen with I assume less documentation.
It was mentioned off hand in a video I was watching while h sparked my interest to learn more. I've since fallen into an etymology hole.
Polari is a fascinating case study into the formation of an unregulated language. How its passed from subculture and changes overtime.
I did notice how words such as fruit and zhoosh are still in the lexicon today, though I suspect very few realize the origins.
Finally, farting crackers is by default the new name of pants.