What makes people more susceptible to colon cancer?

Many factors. You are more at risk if you have 1st-degree relatives who have had colon cancer, or if you have certain hereditary diseases affecting the colon such as familial adenomatous polyposis. Age (older than 50) as well as a history of inflammatory bowel disease, previous colon ca, precancerous polyps, poor diet with high fat, low fiber and deficiency of Folic Acid and vitamin d are risk factors.
Cancer risk. Foremost, genetic background. To a certain extend environmental factors play roles, such as diet with high protein, fat, or carbs. Having a balanced diet with high fiber reduces the risk.