I noticed this incident being very close to a timeline someone posted about Joy of Satan on /pol/, the original poster abandoned the thread, someone came in and started intellectually nuking christcucks, then jannies [those not on reddit suicide watch] or a designated FBI agent moved the thread to /bant/ section, where someone posted about RTR's, the website itself, around then the forums went down. The site was unaffected, but the forum got nuked. My assumption is Tel Aviv tranny cyber division DDOS-ing the forum because they couldn't get in and breach.
I'd suggest ensuring latest forum software, strong passwords, not using the same accounts for all things together, the usual stuff.
Whoever is in the penetration testing business should coordinate with the mods to schedule testing every week for forum exploit and wargames, in case there is something, so that the hole may be plugged and to ensure no breach can happen, to a reasonable degree, as nothing is 100% secure.
As for the DDOS, this may help if applicable:
https://phoenixnap.com/blog/prevent-ddos-attacks