The question in the title: What happens when a maintainer goes quiet I will give what I have already checked below so nobody repeats it.
Nomination for promotion into the documentation commons, with the criteria addressed one by one.
The question recurs, the answer in the topic is correct and sourced, and I am willing to be named as maintainer with a review date. That is three of the four; the fourth is whether anybody objects.
Objections genuinely wanted. A bad promotion is much harder to undo than a bad reply.