I'm sure he did think about the idea of being joined by others...but like a lot of rich peoples conceits, it doesn't really work. A community of hundreds means tens of thousands of interconnections to the outside world who are going to know where this place is. You can't create some isolated survival pocket like that against a long-term problem unless it's something the size of a nation, where you can absorb large numbers of people into your community. And if you do create a nation-state sized sustainable community, you're likely serving as a model for the world and seeing the same things adopted globally.