bluesky can be bought.
mastodon cant, but federating with the big corporate backed ones and lobbying, maybe buying big instances allows big money to defederate with small instances, cutting off the vast majority of big instance users from the rest.
it is the same power gmail and other big ones have over small email providers.
they can filter/block you from talking to the users on big email providers, making is slightly inconvenient for those, but unusable for independents