I've been drunk enough to loose consciousness my fair share of times, but I have never been drunk enough to do something like get behind the wheel of a car. If that point of drunkenness exists for me, it exists beyond the "alcohol poisoning, facedown on the floor" point.
Alcohol is often used as an excuse for poor behavior, but in practice with most people it does not have the power to induce most of the behavior that has ever been attributed to it. For example, I might run my mouth and be inconsiderate of other peoples feelings when too drunk, but when I am drunk, I don't start fist fights. The difference? Being inconsiderate of the feelings of others is something that I sometimes want to do but hold back on while sober; starting fistfights is never something that crosses my mind while sober.
For most people, alcohol does not turn them into a different person. It distorts aspects of who they are, blowing some out of proportion, but it doesn't completely replace their set of priorities and desires with ones alien to them.
This is almost certainly not this persons first time driving while drunk. Almost certainly, this person has driven drunk before, sobered up afterwards and realized what the did, and then did little to nothing to prevent it from happening again. A person who drives while drunk is a person with a carefree attitude towards drunk driving even when they sober.