Vertical descent and burning prior to impact are concerning...
I know everyone is assuming a shoot-down. But, Airbus planes use a ‘fly-by-wire’ system. The pilots have a joystick they use to fly the plane, not a ‘wheel’, like Boeing aircraft do. With most Boeing aircraft, there is still a connection to the control surfaces, so the pilot has some control of the plane in case of a hydraulic system failure. It makes it VERY hard to steer, but it’s there.
What if the fly-by-wire system failed? The pilot would have no control over the plane. Conceivably, the plane could transition to a nose-WAY-down attitude with the pilot not being able to do anything. (Remember, reports are saying he radioed an in-flight emergency due to a ‘technical fault’.)
As for the burned bodies....if a plane, carrying an almost-full load of fuel, slams into the ground and explodes, you bet there will be burned bodies.
I am not totally dissing the idea of a shoot-down, but there are other possibilities. Sabotage? On-board bomb?
(Yes, I know these have been covered.)