when chris finally decided to hike out of the stampede trail what prevented him

There is evidence that Chris makes of things to do before he departed, and it seems clear that he is preparing to return to civilization, and perhaps even join society. A photo he takes of himself at around this time, after shaving for the first time in the wilderness, shows him looking healthy, but already alarmingly gaunt. He packs up all of his gear and starts his hike back to the road that brought him here, but he comes across a three-acre lake covering the trail, where before there was only ice and small ponds. He manages to climb around this, but when he reaches the Teklanika River, he finds what was easily crossed in April is now a rushing torrent which would surely drown him, so he turns back, hoping if he waits it out it will again become crossable.