I'd bet it's a case of sending in batch requests. The office coming up with fake identities sends them all it to the passport office at once and then the passpo

I'd bet it's a case of sending in batch requests. The office coming up with fake identities sends them all it to the passport office at once and then the passport office proceeds to use their normal processes to issue passports and that processes generates sequential numbers in this case because they are processed one after another. Obviously easy to fix, but also seems pretty easy to happen without anyone realizing