My guess is that irritation and inflammation of the airways between the lungs and the throat (from strenuous voice work) increases susceptibility to the virus.
I'm not saying he died of covid. I'm saying it further weakened him.
Where that an even remotely plausible theory then you'd expect choir, opera, and concert singers to be dying WAAAAAAAY before "voice actors", a group who talk no more than regular actors, start dropping from covid, which isnt even relevant for this great man's passing.
I can only hope he has spoken every word such that an AI can perfectly mimic his speech so we can have him as batman forever more once we get to the point where we can mix and match actors in films.