Seems to me the initial strain was likely developed in a Chinese lab, passing a non-human cornavirus around between various mammals, mutating it until they had one that affects humans a lot worse than a normal common cold coronavirus.

Viruses will typically mutate towards less lethal, increases the spread, which would explain why this one has become more like a cold after the first couple months passing through the population.

However if it was produced in a lab (and released in Milan as a test run, then NYC) that means the pure lethal strain can still be deployed. I would bet that's what Trump was exposed to, but I still expect he'll be fine.