Why did Krakauer break his chroological timeframe to include information about both families?

The fact that the reader knows this will be the end from the beginning creates many moments of dramatic irony. The most profound example in this section is when Jim Gallien offers McCandless different kinds of help, and McCandless insists that he will be fine. The reader of course knows that this will absolutely not be the case. This moment is also an early example of one of the book’s motifs—that of moments where Krakauer shows a decision or twist of fate that leads McCandless to his death, moments could have easily gone the other way instead. Another example in this section is Wayne Westerberg’s prison sentence, without which Krakauer implies McCandless may very well have stayed happily and safely in Carthage.