Just to clear one thing up: these weren't AI/LLM crawlers, or crawlers per se.
These were bots requesting the front page (GET /) and immediately closing the connection to do it again and again and again.
This was done by several thousand IP addresses at the same time.
The only goal was to starve resources (Denial of Service) by constantly forcing the front page to be requested through PHP and MySQL. which blocked the pipeline and blocked TCP connections (80K - 100K open connections).
The server itself, while under load, was perfectly navigable for admins, and nothing went down or crashed.
As stated: we will simply take the forums offline and serve a static page when this happens again.
Nobody's life is lost, and it will only hurt temporarily.