What we know so far is that there tends to be vascular damage: the endothelial cells lining the blood vessels are the cells most affected. The longer a person has it, the worse the damage will be. In this case, what doesn't kill you makes you weaker.

The lungs have a huge network of very fine blood vessels which are particularly vulnerable. Obesity and diabetes negatively impact the circulatory system. Some cancers have ACE2 expression which results in higher risk. Thinking of COVID-19 as a circulatory disease is a better model than thinking of it as a respiratory disease.