...all communities named "piracy" are not the same, the full community name technically includes the instance, they are each their own "subreddit." You could subscribe to all of them if you wish, or to just "the largest one," but you can think of them as say "lemmyworldpiracy" and "beehawpiracy" and so on, they are just different communities.

It'd be like if two separate 15yo kids ran a fan page for their favorite anime character and expecting them to be identical simply because they are both about Goku, they're just different "sites" by different people, they just aren't the same thing simply because they're about the same topic.

Again, it's the same in reddit, if you create a new sub no one can see it because reddit doesn't share what new communities there are, they're hidden from the search unless you know the exact name or until they have enough activity, but it's a cycle where you can't have enough activity because it doesn't appear in searches.
The answer in both, reddit and lemmy, is crossposting, you need to promote your new community with good content.
Or sharing it in communities like !wowthislemmyexists@lemmy.ca or !lemmy411@lemmy.ca
There's also this site, tho I don't know how it gets populated https://browse.feddit.de/