It is not a haemoglobin issue as people who were put on blood oxygenating machines were able to be kept alive.

Other people investigating are finding that the Wuhan-virus seems to work with another bacteria that destroys the lung lining so that oxygen cannot be absorbed.

Enough vitamin C seems to stop this.

The reason bats have been being studied is that they don't seem to produce vitamin-C, so how do the keep the disease load down. And they found that the bats make vitamin-C, but only in an as needed way, at the point its needed.

So, the virus cause an immune breakdown, which allows the bacteria to spread in the lungs.

And this is why many penicillins have worked as as treatment.

This is all highly speculative but supported by all the actual data.