I agree that being in good shape generally will help, but I also think there is a genetic component of this which is related to cytokine storm (also goes by several other names). Up to 15% of the population is genetically predisposed to be challenged in this way.

Our CDC / WHO recommendations basically only include supplying oxygen and treating for sepsis (at which point you're probably already cooked.) They recommend against corticosteroids or similar treatment. There seems to be no consideration of this possible catastrophic condition. As a starting point, there are some good articles here:

https://www.uab.edu/reporter/know-more/publications/item/8909-here-s-a-playbook-for-stopping-deadly-cytokine-storm-syndrome

http://www.xinhuanet.com/english/2020-02....

After being contagious for about a week (or 2), followed by a mild cold for a week, the sickness then suddenly goes from "I just have a cough" to dead in about a day. It's estimated 2/3 of the dead in Wuhan died at home.