It's not the breach in the way you think it is though. Think of it as plastering lots of posters on the outside of a bank vs breaching the bank. Scary yes but unlikely to be a risk to your data inside
It's fairly easy to create multiple accounts, and post anything (hence there is spam about all sorts of things at times with multiple crypto coin, scam hair dryer threads popping up), even for someone with zero tech know how.
Last week I could have set up 60 accounts and started spamming with pictures of my dog. It would of taken a while for it to be noticed that multiple threads and comment replies under different usernames were duplicate. I wouldn't have access to anyone's personal data and would have the same account access as everyone else.
This then for professional spammers they do this automatically, simply by having a computer auto generate account info, and posts (no different to when a computer auto fills a form for you or helps randomise your password)
This happens with all websites with co ordinated spam attacks. The tricky thing is that I don't believe that the night watch here have many powers to look at blocking site wide functions, or identifying ip addresses etc. Lots of sites also only allow posters to create a certain amount of activity in a short period, and prevent new accounts from posting photos.
On a site I used to admin, I could turn on controls to limit how often someone can reply, add new keywords to prevent posts with those words from auto publishing etc. I'm not sure night watch have that
Obviously the imagery is completely horrendous and it's right that some sort of statement Is made, police involved etc and longer term review of site safety but the idea the personal data on the site has been breached is likely incorrect