Credential stuffing is the automated injection of stolen username and password pairs (“credentials”) in to website login forms, in order to fraudulently gain access to user accounts.
Since many users will re-use the same password and username/email, when those credentials are exposed (by a database breach or phishing attack, for example) submitting those sets of stolen credentials into dozens or hundreds of other sites can allow an attacker to compromise those accounts too.
Edit: yeah it's just a brute force with less steps. That's fuckn embarrassing
"Credential Stuffing is a subset of the brute force attack category. Brute forcing will attempt to try multiple passwords against one or multiple accounts; guessing a password, in other words. Credential Stuffing typically refers to specifically using known (breached) username / password pairs against other websites."
Just because this method is a subset of the brute force attack doesn't mean that they don't have request limiting. They are reusing known breached passwords from other platforms, which makes it basically a guarantee that they will get the right password if they don't use a password manager. Their computer systems are secure, it's just their business model that's a privacy nightmare.
According to the quote they would've used breached passwords. You don't know anything about request limiting. It wasn't just randomly entering passwords unrestricted, as per your own quote.