Engine failure followed by this kind of massive airframe failure would surely not occur in such a short timeframe that nothing is recorded on the FDRs? Engines are not bombs, they start to malfunction and then they disintegrate. Data would be recorded, and the pilots would see instruments recording odd parameters.
The lack of recorded info on the FDRs (I think we can assume there's nothing to be heard/recorded as they would have released details by now) is very reminiscent of the Ukraine Malaysia airlines incident... Massive loss of all system integrity caused by an explosion.
so if there is no trace of conventional explosive materials, what can cause such a loss of all systems that record what's happening in such a violent and instant way?