I have been following both the track n road circus closely for almost 2 decades and from what I can recall on top of my head, Eliud kinda disappeared from the scene when he left the track scene. I have always been suspicious to this gap in time. When he re-appeared again he seemed quite like a beast.
Dont get me wrong, he was a very strong runner before but not topnotch. There were always a few (Kenny B etc) ahead of him.
One quite crazy theory I have is that looong time ago Nike or some other big Organization scouted him and then approached him (along with several other athletes?), inviting him to be part of their marathon "project". Maybe they could not foresee this kind of success but now its too late to "throw him under the bus" and expose for doping. Simply, they are playing along and milking the cow for as long as possible.