different perspective
Actually no mysteries needed.
Close to IGARI something went terribly wrong, probably leading to or including severe hypoxia for most souls on board. After things calmed down somebody felt it was not a good idea to go home with this mess on board. So he/she decided to hide the mess. Set a flightpath that doesn't touch land again and select south pole as final destination.
One tends to think this was carefully staged, but maybe it was just pure chaos, and in the end somebody decided that the rest of the world better shouldn't know. Even a flightsim geek would be able to program such a flightpath.
Deliberate action to avoid radar? No way. The MAF had them on their radar all the time, they just didn't care. But that was obviously not an achievement of anybody on board MH370.