An injury or illness leading to bed rest can cause clots to form. Clots can just form anyways. High blood pressure. Which, again, becomes increasingly common as people age regardless of fitness level and diet.

The guy lives wholesome lifestyle, but that lifestyle is not that terribly healthy as people want it to be. Simple lifestyles are not always the most healthy thing you can do. His diet is limited by habit/routine, but also possibly by cost and additional effort it would take to cook more healthier. He already works a lot and healthier food woold require more effort.