"In the 20th century alone, malaria claimed between 150 million and 300 million lives". And thats probably conservative. I have no idea why you think 80 million died from ALL diseases over the 20th century.

There were approximately 12 billion people who lived in the 20th century...most people don't die of old age (i.e. even if you take your 200 million dead by democide, that means 11.8 billion people still have to die some other way).

Cardiovascular diseases, infectious diseases including things such as prenatal infections, cancers...although we didn't really track these that well in the 20th C.

In the developed world cardiovascular/cancers/infectious diseases still wiped out the most. Then in developing worlds it was much more based on infectious diseases, malaria, water contagions etc etc etc etc.

Not to mention, a HUGE % of the people who die in war situations...its because of disease. Its not the shooting or bombing itself. It's that access to proper health care becomes almost impossible. You can count that in the tally of democide, but disease is very clearly playing a vital role there too.