Last Seconds
Based on the photos and analyses on the metabunk site, I think that we can reasonably assess the sequence of the plane's last seconds.
The large number of missile fragments penetrating the aircraft's frame would have caused instantaneous depressurization. The pilots would have been mortally wounded by the fragments penetrating the cockpit. Likewise, many passengers. All that will be established in post mortem examinations.
The plane's systems would have been disabled and it would have been uncontrollable. It disintegrated in the air.