the old boy network is very much alive and living in Phoenix and they likely were very tight. When I say the OBN, I mean not just business but the media (at the time run by the infamous Quayle/Pulliam family) and politics, too.
It's still a very tight closed community, too.
Anyhow, it's very likely Keating himself may have introduced McCain to Cindy Hensley. McCain came out of the Hanoi Hilton with politics on his mind, he says as much in his biography. It's well known that he was married at the time and Keating would no doubt have known it too*, but Carol (McCain's first wife) was in no position to further McCain's political ambitions (no family connections and I would dobt anywhere near the kind of money Cindy had). No doubt Keating smelled opportunity all over the place and you have to know he's a damn shrewd one (BTW, he is still alive).
That's a start. I'm slowly trying to piece together more about the whole story but unfortunately so much occurred before the 'met happened that I can only get bits and pieces; it just isn't that important for me to put footwork into it--sorry.
The best coverage of McCain in any newspaper is from Phoenix New Times, look especially for coerage from Jana Bommersback and Amy Silverman; link:
http://www.phoenixnewtimes.com/*FWIW, Keating is a notorious raving social conservative and was a large part of the funding behind "The Silent Scream," the notorious anti-abortion propaganda film.