Why did Chris McCandless go into the wild?

The
two reasons that you have listed are good reasons for why Chris McCandless wanted to go out into
the wilderness. Keep in mind that McCandless's passion to be out in the wilderness did end up
killing him; however, he also managed to survive living in the wild for quite some time before
he even began his Alaskan debacle. McCandless passed away during the trip, so Krakauer couldn't
ask him why he chose to live like that. Readers are left to come up with our own reasons, but
McCandless's letter to Franz is really good support of the two reasons that your question has
already listed.

The very basic core of a mans living
spirit is his passion for adventure. The joy of life comes from our encounters with new
experiences, and hence there is no greater joy than to have an endlessly changing horizon, for
each day to have a new and different sun.

Notice how
McCandless emphasizes the passionate pursuit of adventure. He longs for the endlessly changing
horizon. McCandless continues his letter...