Any citations on the numbers? I assume those aren't just the number of smokers who died from lung cancer or something as silly as that. Did you factor in the fact that air pollution kills a lot of people and is also caused by people (and cars as in your example) in different ways, for example by being one of the causes for Cardiovascular diseases(so is smoking, yes) which are the most frequent cause of death? Does pollution kill less people than tobacco? I mean you are saying that it isn't even close so you probably have, but I would not take such statements at face value without more data.
The man-made object responsible for the most deaths worldwide is the tobacco cigarette. It isn't even close.
Tobacco kills 443,000 Americans a year and 5 million people a year worldwide. This is more than the total number of people killed by cars and firearms combined. Cars kill about 32,000 Americans each year and 1.3 million people worldwide, while firearms kill about 32,000 Americans each year and "several hundred thousand" people worldwide.
100 million people were killed by tobacco in the 20th century. This is more than the death toll from World War 1 (17 million) and World War 2 (50 to 70 million) combined.
From a strictly utilitarian perspective, would there be anything to be gained by, say, starting a campaign of assassination against executives of tobacco companies?