Anything beyond, any assumption on the plane having been taken over completely in its navigational and communication abilities by some yet unknown force or forces, is too much of a conspiratorial theory to me. Into which I refuse to engage at this moment in time.
And then, sorry to say, almost everything except of a clear motive, point to some deliberate action of the crew or parts thereof.
I wholeheartedly agree, judging by the series of events leading up to radio silence and switching transponders off and the path and flight time time beyond those events, this was very likely an intentional crash by some party with flight experience and access to the cockpit.
We can only guess at the motive until we have more data, but all the current evidence strongly suggests that this was not an accident.