are there reasons?

There's no single answer. Risk factors include the usual culprits (smoking, red meat, not enough veggies, too much fat, alcohol). A quick google search will show a number of things that may be linked to an increased risk of colorectal cancer (mainly diet), but it is not at all unusual for someone youg and healthy to be diagnosed with it. It is the fourth most common cancer for men. (source: Men's Health - Top 10 Health Concerns of Men - Cancer ) . Even so, you may have none of the risk factors and still get colon cancer. I hope this helps!
Aloha, RH