The Fediverse is decentralised for many reasons:

• It stops anyone buying the Fediverse out. There is no central server, so there’s no single thing anyone could purchase in order to take over the network. Twitter-Musk scenarios aren’t possible on the Fediverse.
• It promotes higher quality moderation. Smaller servers tend to have higher quality moderation, because they have a much larger staff-to-member ratio. On massive servers, the number of staff per user is very low and the moderation quality tends to be much poorer.
• It empowers the user. If the people running a Fedi server do something bad, users can move their accounts to a different Fedi server without losing their followers. This discourages server owners from doing anything bad in the first place, and gives users lots of options if the worst happens.
• It lets anyone start their own server, even non-technical people (click here to find out how ⧉). The simplicity of a small server means it only costs about $8 per month from a managed hosting company which does all the technical stuff for you ⧉.
• It means each server can make its own rules, so if there are any disagreements people can move to a different server with different rules, or even start their own server with rules they write themselves.
• If one server goes down, other servers keep working. Problems on one server don’t bring down the whole network.
• Servers don’t all have to use the same software. This diversity means if one kind of software doesn’t work properly, it doesn’t affect the whole network, and servers can switch to other software if they want. The diversity also allows servers to specialise in particular kinds of content for users who just want particular features, for example PeerTube specialises in video publishing, BookWyrm in book reviews etc.