Seriously? You don't know HOW he did it but for the record, most of us are not that dumb.
There are only so many ways to get from point to point WITHOUT (key word, stay with me now) others aiding you.
A bike or a car and then run only small parts of it. Is there another way? Does he own a rocket? Can he turn himself invisible? Wake up people.
In Boston he was walking on the side of the road with no number and looking down. Can you not figure out the simplistic reason as to why he was doing that? He crosses a pad and off he goes to the next one. Not rocket science or anything even remotely close. The problem is you want to hear him say it so it's official, right? The truth, he's laughing his butt off at the notoriety that he's received, albeit bad.
Bottom line, he didn't do anything criminal and worse case he can claim that he must have went off the course "accidentally", aka no intent, and give back money if there was even any money involved.
Why did he do it? To say that he's faster than he is and brag about it. Pictures and video show that he's not a 2:52 marathon when he starts where he starts and ends up with different shoes at the finish line. Who does that and where were the shoes at? He cheated and he probably thought he would never get caught. If not for the internet he would have gotten away with a lot more than he did. Story over and no big surprise, he cheated as many do, but he did it often, just not the level of Rosie Ruiz or Oscar Miranda. Enough said.