Luckily password hashes aren't much valuable to crack them. Well, they allow one to iterate through a whole lot of potential passwords without having a server to respond to it if they know the algorithms. So they are convenient, but possibly insufficient.
Sounds like there was an SQL injection vulnerability in gab that allowed them to get access to a bunch of data including password hashes.
Luckily password hashes aren't much valuable to crack them. Well, they allow one to iterate through a whole lot of potential passwords without having a server to respond to it if they know the algorithms. So they are convenient, but possibly insufficient.
Care to explain more? Are you talking about common password databases a.k.a rainbow tables? It looks like they did just that.
If the hashes are properly salted rainbow tables are not a problem.
This just allows them to attempt brute forcing individual passwords without being rate limited.