HN automatically determines when posts are "dupes" and merges them, based on a number of criteria. Those previous submissions didn't get much traction, so the submissions weren't merged. In fact, sometimes HN automatically resubmits posts on your behalf. There's nothing unfair about a submission being posted by multiple people.
If you're worried about astroturfing, email the mods and they'll take a look.
i'm starting to think it's some conspiracy, reddit is famous for having created fake accounts to fake engagement and activity to get the site off the ground. do we really put this type of stuff beyond the guys at openai? i don't.