Based on his words and actions, I can only believe that he climbed Mt. Everest, and thought: "Is this all there is?"
I would imagine that being on the PGA tour involves a lot of people kissing your a** with their hand out. When you reach that highest achievement (winning a major or being #1), it can be thrilling, and then the obligations set in. I think that golf culture, and our obsession with it, could leave a subconscious belief that as soon as I'm #1, I will ascend to heaven for all eternity. Cue trumpets and angels.
Ain't so.
I think we are so conditioned to place social and business achievement above all else. He got to the top, and realized: This is a lie, and our time on earth is more important than 'accomplishments' for other people's gain.