maybe examine the prevalence of all those conditions in the US?
What were the most common pre-existing conditions?
"More than 75% had high blood pressure, about 35% had diabetes and a third suffered from heart disease."
How common are those conditions in the United States?
High Blood Pressure - 1 in 3
Diabetes - 9 in 100
Heart Disease - 1 in 10
It seems times are changing: https://www.cdc.gov/bloodpressure/facts.htm
We have "evolved"!
Now you propose that the underlying condition most present isn't really a condition.
I found https://www.epicentro.iss.it/ben/2002/settembre02/2_en (the same health institute that provided the study I was talking about above). I quote:
"The prevalence of borderline hypertension was calculated by determining the number of persons who had systolic pressures between 140 and 160 mm Hg or who had diastolic pressures between 90 and 95 mm Hg."
This is more inline with what I've been thought in med school in my time.
I suspect age and immune function drive mortality, and the other factors are merely along for the ride.
[1] https://www.uptodate.com/contents/treatment-of-hypertension-...