Anybody with experience would have realized that it could easily mean his own death if he shut off the fuel flow. The fuel would have had to been shut off some little time before the plane started its way down the runway. Could a saboteur have left the plane before it started its runway journey?
Unlikely with so many eyes and cameras around. I would not prioritize considering very improbable if not implausible scenarios just yet. People need to learn some patience. This is a big disaster both for India and for Boeing, I don't think they can afford a coverup of any kind.