Clarification: the protocol is ActivityPub.
Lemmy is open source software built on the protocol. (Kbin and others are different sofware but also built on Activity Pub)
Instances, Lemmy.world, and Sh.itjust.works are clones of Lemmy running independently but federated.
Now say it again but replace crytpocurrecy with Website aggregation. Its honestly not that different from leaving the big centralized reddit for the Fediverse… only to mostly end up in a few relatively huge alternatives in the name of decentralizing. Its just… human nature.