Monero isn't like the other three, it's P2P with no single points of failure.
I haven't looked too closely at Nostr, but I'm assuming it's typically federated with relays acting like Lemmy/Mastodon instances in terms of data storage (it's a protocol, so I suppose posts could be local and switching relays is easy). If your instance goes down, you're just as screwed as you would be with a centralized service, because Lemmy and Mastodon are centralized services that share data. If your instance doesn't go down but a major one does, your experience will be significantly degraded.
The only way to really solve this problem is with P2P services, like Monero, or to have sufficient diversity in your infrastructure that a single major failure doesn't kill the service. P2P is easy for something like a currency, but much more difficult for social media where you expect some amount of moderation, and redundancy is expensive and also complex.