Because he swung the club harder than anybody in his youth which allowed him to crush and devastate golf courses like MJ did on the basketball court, or a better comparison, the Williams Sister dominating the tennis courts. This can explain his physical deterioration to some extent, but athletes come back from injuries all the time. The mental aspect is a) more of an impact on the player and b) harder to explain because nobody except Tiger really knows. But ESPN put out this pretty compelling article a few years back explaining how Tiger started to slip after his Father's death. Good read.
The Secret History of Tiger Woods

Y'all don't think Tiger BEEN back to fukking these hoes?
His body is shot. And the real problem is people just won't let it go. It's been YEARS since Tiger was "Tiger" people gotta let it go. It's like expecting Roy Jones to become the pound for pound king again.
Duh nikka, I went comedian to get some daps. He's hurt, been overdoing it in training for years.Dude fell in his backyard and couldn't get back up until his niece found him. Beyond everything else, he's just physically broken.

yeah, he too busy thinking about white trash waitresses to smash in parking lotsGolf a mental game and he not there mentally no more