There are probably several factors that are involved. Chronic levels of inflammation will affect the lining of the arteries. This can play a role in blockages that may lead to strokes.
Intake of trans fats and other toxic oils may play a role both in adding to inflammation and blocking arteries.
High levels of cholesterol have not really been found to be an issue, so much as inflammation.
Arterial stiffness can be a factor. This may be linked with nutritional deficiencies.