Don't see why.
Smoking or buying stock is not a disease itself. ;0)
I would say it's a given many cancer surgeons smoke themselves, much less have purchased tobacco stock for which cancer itself isn't attributed solely and exclusively to smoking and the use of tobacco products.
This is the Center for Disease Control, not a center for the elimination of tobacco companies.
Smoking can become an addiction. Addiction is considered a disease.
Addiction as a Disease
"The consequences of untreated addiction often include other physical and mental health disorders that require medical attention. If left untreated over time, addiction becomes more severe, disabling and life threatening."
Oh also, she did resign so there's that.