That however would be a different problem. A horizontally scaled instance would be able to cope with more users, but if it shuts down for monetary, personal, or whatever reason, it’s still down.
Protecting a community from this is what the decentralized part is for. That is already in place.
(Although there is a middle ground where you could design the system in a way that one instance is mirrored and load-balanced across different hosters. That would actually also be quite interesting to have. But that’s another layer of complexity on top.)