Maybe he drank himself to death to forget that he had become "Thomas Kincade, Painter of Light."
Put yourself in his shoes for a second: You're a painter, maybe a pretty good one. You hit upon a style that people can't get enough of, it's like minting money. You're a clever fellow with finances, know some bankers who can line up capital, and you create a mammoth commercial empire selling sparkly junk as fast as you can crank it out. Now everyone knows you as that awful hack with Snow White landscapes in shopping malls. This wasn't quite the way you thought it would turn out. You really wanted to be on the wall next to Warhol or Jasper Johns. You used to be a pretty good painter, but everything's gone horribly, bizarrely wrong.