There are several things that led to Chris' fate, but i think the main one is a theme in many novels, and that's man versus nature. Although Chris lived off the land, he didn't give nature the respect or thought necessary, and didn't plan well enough. Without enough food, Chris starved to death. He believed he could live off the land without thinking about nature's cruelty. The dangerous currents of an unforseen spring-run off, and a lack of food contributed to his death. His insistance to do things his way (no hunting gun, no information about where he was going, no map!) left him defensless when nature turned out not to be friend, but to be foe.