No, McCandles was not trying to "survive Alaska" and write a book to become famous. In his last letters before leaving for Alaska, he told his friends that he was going to go up to Alaska to just spend the summer in the woods, as a final little adventure before coming back home. His mistake was that he viewed a little trip to the interior of Alaska as being exactly the same as all of his other little trips in the lower 48.
McCandles was from a very upper middle class family, with plenty of money, and he had absolutely no interest in getting rich. Had he wanted to do that, he would have just gone to law school and practiced at a big firm in downtown D.C. (Starting salaries for law associates in those days was about $125,000 at the big firms. Much higher now) As a matter of fact, during his two years before going to Alaska, he wandered around and worked many low paying, filthy jobs.
As to the poisonous plant, from the book I understood that one of the factors that killed him was that his plant book said that the root bulb of the plant was edible, but it failed to say anything else. In his diary, he said that he ate not only the root, but also the pods that grew on the stems (holding small peas). These, it turned out, were very poisonous, full of alkalie. Once it was in his system, he was unable to flush it out, and he died a slow death.
He knew he had been poisoned, and tried twice to walk his way out back to a highway, but was too weak and sick to do it. A small stream he had waded through to get to his camp had turned to a roaring river (from summer melt), and it was impossible for him to recross it. Had he taken with him a U.S. Forest Service Map, it would have shown him that just a few miles up from where he tried to cross, there was a cable streched across the river, with a movable car on it, used by the Rangers. He had a map, but it was just a regular highway map from a gas station.
His only firearm was a Remington Nylon 66, .22 rifle. He killed a moose with it, but had never butchered an animal. Instead of cooking up the fat or the liver (to help recover from the poisoning and starvation), he tried to cut "steaks" off of the haunch, and then tried to smoke several large pieces, in the late summer. All of the meat rotted in about 3 days. He killed and ate alot of squirrels, but the lean meat didn't help him.
Why would someone call him mentally ill? He did exactly what everyone "talks" about doing, but never does. He acted like a totally free man, in a free society, with no debts, with no chains or bonds, and came and went as he pleased. People always talk about freedom, but when someone actually does it, society labels him as crazy.
McCandles didn't just walk into the woods in Alaska. He followed an old secondary gravel road into the forest for about 12 miles, and then followed an old bulldozer/truck trail from a mining camp for another 8 miles or so, where he camped in a deserted bus. The road he was on was still in use by hunters, and indeed, he was found a few days after his death by a group of moose hunters who used the road (and camped in the bus) every year.
We can fault him for being unprepared and dying in the wilderness, but his faults were small. No forest service map, and eating a part of a plant that he thought was edible. How many hundred mountain men died in the wilderness from far bigger blunders?
Mannyrock