The rear pressure bulkhead was blown out rearward, causing the tail to blow off, IMHO!!! Something odd occurred inside the passenger fuselage.
Oh, but no way will they even say the word, terrorism...
I don't know about that. A bomb of that scale in the passenger compartment should have caused horrible pressure trauma to the passengers, along with flash burns. Doesn't seem to be the case.
Either the tail was knocked off by a nose-high touchdown short of the runway (simple, Occam's Razor explanation that seems to fit the early data) or was blown off by an external force -- SAM (less likely).
If there is verifiable information that heavy engine or fuselage components are on the ground in or in the water well short of the touchdown point then #2 seems more likely.