Krakauer seems to to suggest that Walt's past helped push Chris toward his chosen future. As Chris nears the end of his time at college, he grows more and more distant from both of his parents. But it is Chris's father that Chris really seems to grow apart from. It's important to note that Krakauer is not Chris McCandless, so there is no way to know for sure why Chris suddenly began distancing himself from his father. Krakauer suggests that Chris grew disillusioned with what he saw as his father's hypocrisy. That manifested itself in two ways. First, Chris very obviously felt that his father's money could be put to better use than what Walt was doing with it. That's probably why Chris decided to give away the remaining $24,000 of his education money.
The final two years of his college education had been paid for with a forty thousand-dollar bequest left by a friend of the family’s; more than twenty-four thousand dollars remained at the time of Chris’s graduation, money his parents thought he intended to use for law school. “We misread him,” his father admits. What Walt, Billie, and Carine didn’t know when they flew down to Atlanta to attend Chris’s commencement—what nobody knew—was that he would shortly donate all the money in his college fund to OXFAM America, a charity dedicated to fighting hunger.
Second, during one of his summer wanderings, Chris discovered that his father was still in a relationship with his first wife. It hurt Chris deeply, and Chris wanted nothing more to do with his dad after that.
After Chris unearthed the particulars of Walt’s divorce, two years passed before his anger began to leak to the surface, but leak it eventually did. The boy could not pardon the mistakes his father had made as a young man, and he was even less willing to pardon the attempt at concealment.
I suppose there is an implication that Walt drove Chris away, because of his marital indiscretions. But I don't believe that. I think Chris would have gone on his journey either way. I think Walt just made it easier for Chris to emotionally check out and leave his family.