Sorry, but I'm not speculating.
I've got good info about the ONLY communication.
It was
me speculating, based on your information
The first action any pilot should take following a decompression is to get the mask on. Not descending, not trouble shooting, just get the mask on.
(later you can do the rest...)
If it's true that the communication was of poor quality, that could indicate the pilot did exactly what he was supposed to do - i.e. got the mask on. Speaking through the mask microphone may produce a lot of static.
The mystic part is that didn't prevent the pilot becoming incapacitated, hence I was speculating there was no O2 coming to the mask. If the masks are of the same design as airliners - diluter demand - you will still breath air but it won't be enriched with O2.