I don't actually know what the bus factor for Tarsnap's infrastructure is. 2 is just the absolute lower bound from what I know of the company itself. It is in all likelihood much higher.

I can't read the founder's mind, but if I were them I would probably have some Kongō Gumi style designs on making it a 1000-year company just because that's a fun intellectual exercise. [1]

[1]: https://www.tofugu.com/japan/oldest-businesses-in-japan/