He was probably on Ambien and fell asleep at the wheel. Not the first time Tiger fell asleep which ended in an accident. Doubt if it will ever be confirmed because of the lack of testing and the none action of the Sheriff's department.
Thankfully no one else was hurt. It was Tiger who paid the penalty of his accident. A recovery that will allow him to return to golf at the highest level will require a huge effort and pushing himself through considerable pain, and even then there will be no guarantees.