1. The engines did not self-destruct.
2. The vertical stabilizer snapped off at six tremendously strong carbon fiber composite structures at the same moment. No bolts missing.
3. The vert stab was not blown off by a bomb - it looks undamaged.
4. There was fire and/or an explosion toward the front of the plane before the tail came off, according to eyewitnesses, which is not an ideal indicator, but remarkably consistent, recorded by the media on the spot, and at least some of the witnesses sound credible.
And I think we can eliminate turbulence: The plane made a tight turn just after takeoff. The forces from the rudder on the vertical stabilizer would have been several times the maximum possible force exerted by turbulence. So if the composite attachment points were weak for some reason, the plane would never have completed that turn.
So my vote for what took parts off the plane is: an "unusual attitude." Something got the plane sideways so that air load snapped off the tail, and the engines. And that something probably had to do with whatever the eyewitnesses saw.
One thrust reverser deploying in flight would do this. Although I think that would show up on the cockpit voice recorder in the form of two men simultaneously shouting, "What the Hell?"