So they're talking hospice already.
No cancer in his brain, but (and I'm only relaying second hand info here) it sounds like because of how aggressive and serious his covid was, it led to the cancer popping up, and because he's on dialysis chemo probably won't take for this particular cancer. And it's late stage and very aggressive otherwise.
So the proximate cause isn't covid, it's largely influenced by the infection he had. So a big "get fucked" to anyone minimizing the effects of covid still.