How does Chris McCandless keep people at arm's length?

In the nonfiction text Into the Wild, written by Jon Krakauer, Chris McCandless is able to keep people at arm’s length by constantly abandoning relationships with people who started to get too close to him. This behavior is first seen when Chris sets on his journey, without telling his family that he has left, or even revealing where he plans on going. While Chris had a rough relationship with his mom and dad, it is shocking that he would leave without telling his youngest sister, who was someone he was very close with. However, this behavior is further reinforced throughout the text when we see him build strong relationships with others in which he ultimately ends up leaving. Chris’s ability to keep to himself also further supports his ability to keep people at arm’s length. As revealed by his sister:

He was very to himself. He wasn’t antisocial— he always had friends, and everybody liked him—but he could go off and entertain himself for hours. He didn’t seem to need toys or friends. He could be alone without being lonely.

Chris was fine being on his own and enjoying the nature around him. He didn’t need the companionship of others to make him feel important or loved, rather he was content living a life that focused around his own aspirations.
Given Chris’s ability to survive on his own, without deep human relationships, he was ultimately able to keep people at arm’s length by continuing to enjoy the relationship with himself. Although Chris does stay in contact with some of the people he meets on the journey, by sending postcards every now and then, he ultimately uses his ability to get up and leave as a way to keep people at distant lengths. In doing so, Chris further forces his relationship with himself and nature, in order to make up for the lack of relationships he creates with others.
With the advancements of technology in the years after Chris’s journey, it may be hard to imagine how Chris would be able to keep such distance from others in a time where there is now constant connection. However, it is important to remember that there were still telephones when Chris decided to leave. Although Chris wrote postcards and letters, ultimately Chris decided how he would communicate with others, and in doing so he was able to keep people at arm’s length.

One way that Chris McCandless keeps people at arm's length is by living a nomadic lifestyle. McCandless never really gives himself or other people the chance to get to know him on a close personal level because he moves on to a new location before that relationship can mature. There are people in his life that he does get relatively close to like Ronald Franz, but even that relationship is kept distant by McCandless himself when he leaves.
The other way that distance between McCandless and other people develops is by people thinking that McCandless is a nice enough guy but a bit weird too. A good example of this can be found in the section of text where Krakauer narrates about McCandless's college experiences. McCandless, like many other college students, is passionate about injustices in the world around him; however, McCandless seems to take it just a bit too seriously. Consequently, some people feel uncomfortable around a guy that refuses to join a fraternity, doesn't accept or give gifts, and hangs out with homeless people.