For several reasons:

- Nostr is generally much lighter; it can even be served behind Tor without having a public IP, there's no need to maintain a web server etc. There are compact, self-contained relays like Haven, for example, which are a single go install-able app that includes everything needed on the server side, with practically zero setup.

- There are various clients, including mobile and web as well as desktop, which is enough to satisfy pretty much everyone's tastes.

- There's also an economic model that could be the future of journalism: everyone publishes what they want, and those who enjoy it can make micro-payments, if they wish, to support the publisher.

For now, it's a toy with many abandoned experiments, while Mastodon is a walking dead, having never really taken off. In other words, as they stand, neither of them is working. But Nostr has the potential to become the communication hub for many; for instance, there's already a Matrix-like service (0xchat and potentially whitenoise) that supports chat, audio, and live video, requiring only Coturn and a Nostr relay. There's also "long form" support, meaning personal blogs all on the same technology.

In other words, in a short space of time, on Nostr you can have:

- A personal blog-style site

- A personal Twitter/X

- Personal chat with audio and video

- Private notes if you need to jot something down on the go

- A search engine and address book that could allows with different access levels, a real address book usage for personal contacts.

Potentially all in a single, complete and lightweight deployment. There isn't the burden of federation, which makes many hesitate to activate it because, depending on who they federate with, they find a massive amount of resources consumed. It's essentially text, binary blobs, and near-real-time communications all in one. Haven is the first piece of the puzzle, MOAR is the successor in the making, but eventually, there will be one that integrates 0xchat and a web client, all-in-one.

The Fediverse hasn't achieved this and doesn't have the characteristics to do so.

Then again, if we're honest, the old Usenet did it better, but it's dead to most people, whereas Nostr is alive. People only dislike it because it comes from a crypto community, and many are biased against anyone from that world regardless.

X Randomly Banning Users for "Inauthentic Behavior"