If you find them interesting try setting one up! Id be sure to follow as i also have enjoyed those communities!

But yes good question overall from what i can tell the more posts one community gets the more attraction it will pull. Reddit would of been similar in the early days when multiple communities existed for the same thing.

I suppose having similar communities split across multiple instances is the essence of a federated system. People will gather in communities they feel comfortable.

Sauce or some kind of smoothie

Pretty crazy tbh stuff like that goes on