Think of him, instead, as The Last Man On Earth, a scavenger surviving on the belongings of others.
A true hermit would either be self-reliant or would survive on the charity of his neighbors. Reading the article it seems as if he made some attempts early in his time in the woods to live off the land, but Maine isn't a friendly state for such an existence, at least not in the killing cold months. This fellow didn't farm, didn't forage for natural foods á la Euell Gibbons, didn't fish or hunt. He stole. He was a jackdaw, a magpie.
Nor does it sound as if he formed any coherent philosophy or had any soul-searing revelations; no epiphanies. He was too busy surviving - - by stealing - - to do that.
In the end it sounds as if he were one of those people who just wants to be left alone, and made it happen for 27 years of his life. In truth, though, with surviving family, he could have done it in a way that wouldn't have required his breaking the law; easy enough to buy a small plot of land in the wilderness, and have one of his brothers bring supplies once a month or so. His needs weren't so exotic that his family couldn't have afforded to support such a lifestyle. Probably he never thought of asking, or thought he would be refused.
h/t Christopher Eger.