So what caused the breakup?
While it is true the British comet suffered from decompression via fatigue failure of window cutouts, since that time every passenger jet has been designed to avoid that kind of failure as to major structural damage tearing the plane apart due to large holes such as doors, windows, cargo doors , etc coming apart.
For example Aloha Airlines Flight 243 (AQ 243, AAH 243) was a scheduled Aloha Airlines flight between Hilo and Honolulu in Hawaii. On April 28, 1988, a Boeing 737-297 serving the flight suffered extensive damage after an explosive decompression in flight, but was able to land safely at Kahului Airport on Maui. There was one fatality, flight attendant Clarabelle "C.B." Lansing, who was swept overboard from the airplane. Another 65 passengers and crew were injured.
The safe landing of the aircraft despite the substantial damage inflicted by the decompression established Aloha Airlines Flight 243 as a significant event in the history of aviation, with far-reaching effects on aviation safety policies and procedures. look at the photos !!
Look at United Airlines Flight 811 cargo door failure for another example
Turkish Airlines Flight 981 cargo door faiied- but the plane crashed because the differential pressure between cabin and cargo failed the floor which cut or damaged or fouled up the control cables . Since that time, major vents in the floor to cargo area have been standard design practice.
MH 17 was hit by a missile- in the cockpit- and no doubt started a decompression process- but it was unlikely that the decompression did much structural damage in itself. Loss of control at 400 mph with a badly messed up aerodynamic shape most likely resulted in major climb, turn,yaw, spin, dive, roll flight path at many g's above design ultimate loads of around 3 gs or so.
Lets stay focused on who fired the missle, why, rather than bucu speculation as to the details of just what the final seconds of ' flight" were like - especially
without a detailed part analyis available only by investigators.
It was NOT pilot error, mechanical failure, design flaw, or any other unk unk failure affecting other aircraft or that model.