I'm not trying to "tear apart the dead" nor to "judge them for their life choices." 

I worked for years exclusively with homeless mentally ill clients. I cared for them a great deal and a most cared for me, for years after I left the field in fact, and their living situations were almost universally hugely improved.

McCandless was not the person in the Krakauer book, nor the Penn movie.

He was socially disabled and had serious mental problems. 

Craig Medred, who discussed McCandless at length with clinicians, did a useful analysis:
http://www.farnorthscience.com/2007/10/13/media-watch/into-the-wild-the-false-being-within/

Chris McCandless, "Alexander Supertramp," certainly suffered from delusions of grandeur and alienation. I'm guessing he was experiencing a schizophrenia spectrum disorder. He wasn't Thoreau, on Emerson's property and only slightly out of the range of social interaction on Walden Pond. McCandless was completely unequipped for his adventure.