Well, you could be right. Since I was running Bureaucracy+Representation, I was concerned about the stability hit from a 9th city, as well as from owning one more set of tiles outside my homeland, as well as the instability hit from either razing the NEXT Arabian city, or from cultural pressure from that next city. In contrast, in the winning game Jerusalem (which I did capture) was a double holy city under Free Religion, with a larger distance to Mecca, so it was never under significant cultural pressure from Mecca. Finally, Mecca wouldn't have contributed that much; it's not that great a city, and Babylon did 80%+ of all the research. 8 cities is the minimum for Channel Tunnel, Summer Palace, etc. That said, I ought to have been able to pick up Mecca late in the game with no big stability problem, since after Commonwealth my stability gradually crept up to Stable and eventually Solid.
I added a low-spoiler mini-guide to the Wiki.
