I've watched the video of the plane explosion a few times now.
We are seeing footage of after it was hit by something. (Even terrorist inside plane?)
The pilot(s) I think had control of the plane as it descended at a landing glide. It is trailing either pieces or fuel as it follows the path.
Towards the end if it was hit by another missle, I've seen others ask why they would do that?
Simple answer: No living witnesses on board. The pilot might have had a decent shot at landing in a field.