Problem is that inactivity is also known to cause blood clots and subsequent problems, hence deep vein thrombosis being linked with long distance flights. What

Problem is that inactivity is also known to cause blood clots and subsequent problems, hence deep vein thrombosis being linked with long distance flights. What happens during lockdown, people stop moving about and spend all day sitting at home. I think we need to be apply critical thinking to claims of the form, "some one recovered fully but then was struck down by covid19 a second time". That can easily be a correlation/causation fallacy.