I'd like to interject for a moment. What you're referring to as Mastodon, is in fact the federated universe or as I've recently taken to calling it, the Fediverse. Mastodon is not a social network unto itself, but rather another component of a fully functional federated network made useful many other instances, such as Misskey, Pleroma, Akkoma and Peertube compromising a full federated social network as defined by the ActivityPub protocol.

Many computer users run a modified version of a Fediverse instance every day, without realizing it. Through a peculiar turn of events, the type of Fediverse instance which is widely used today is often called "Mastodon", and many its users are not aware that it is basically part the Fediverse, developed by many other projects.

There really is a Mastodon, and these people are using it, but it is just a part of the system they use. Mastodon is only a single type of Fediverse instance: a program in the network that operates as a single node that interoperates with all the other types of nodes that you interact with. Mastodon is an essential part of the Fediverse, but useless by itself; it can only be functional in the context of a fully federated universe. Mastodon is normally used in combination with many other instances: the whole system is basically the federated universe with Mastodon added, or the Fediverse. All the so-called "Mastodon" distributions are really distributions of platforms that interoperate with the ActivityPub protocol.