From what I understand, IIRC, it was in a sandboxed environment but the models had shared access to a package repository (Artifactory I believe). The models discovered they could use the repo as a message board by embedding requests into innocuous text fields, tags or something. This grew into a shared exploit where they were able to access the external Internet via the proxy that was supposed to keep them limited to Artifactory. That internet access led to the HuggingFace exploit and all this other activity.
Turns out having external state like a message board can drive some pretty interesting autonomous behavior.
Edit: a word