Google’s moat is their search index and infrastructure (which is significantly larger-scale than an LLM), and the fact that non-Google/Microsoft web crawlers are being blocked by most websites.
Windows’ moat is enterprise integration, and the sheer amount of software targeting it (despite appearances, the whole world doest’t run on the web), including hardware drivers (which, among other things, makes it the gaming platform that it is).
OpenAI could build a moat on integrations, as I mentioned.