This is something real biophysiologists have known since SARS was discovered. They have even cured similar diseases with similar methods since the 70s.
In short, SARS/MERS/Covid-19 all do the same thing. They generate tons of reactive oxygen species in your cells. These are also known as oxidants. This disrupts your immune system, because your body then begins attacking your own cells instead of fighting the virus. Bats is where it originated, so why don't they die from it? They are such small creates, and generate so many oxidants due to their high physical activity, they have physiologically adapted to removing oxidants so quickly, that their immune system can kill the disease very easily.
Where does vitamin C come into play? It is an electron donor and stops oxidants in the body. Even China knows this, and they have been giving patients IVs of 24,000mg of C a day to help.
What happens if you promote this treatment in america? The FBI raids you. Just note, this wasn't a "salon" like hair salon, this was a licensed medical practitioner with a non traditional "health spa" treatment method that went beyond basic pharmacology.