Well, to be fair, I may have jumped to conclusions by calling it an "explosion". Something disassembled itself for sure, but it may have just been the bell nozz

Well, to be fair, I may have jumped to conclusions by calling it an "explosion". Something disassembled itself for sure, but it may have just been the bell nozzle rather than the whole engine (combustion chamber, turbopump, etc.). SpaceX is calling it an "unplanned shutdown", but it's unclear at what point the shutdown was commanded. It's possible that some off-nominal parameter triggered an engine shutdown, at which point the sudden vacuum inside the engine bell would have caused the nozzle to collapse. (Note that this happened at Max-Q, the moment of maximum aerodynamic pressure, so the outside force on the nozzle would have been significant). This would have had some impact on the aerodynamics of the vehicle (with the flight dynamics software compensating perfectly), but it wouldn't really have been a threat to the other engines, and is not too dissimilar from some unplanned shutdowns which the Saturn V experienced. It wouldn't really count as an "explosion". It might just be a (relatively benign) software bug which triggered the shutdown. On the other hand, the engine might have disassembled itself first, followed by the shutdown order to keep it from dumping uncombusted propellant. This would be an actual explosion of the engine -- contained by the kevlar shielding to keep it from damaging the surrounding engines. If this is the case, then it's a huge validation of SpaceX's RAID-like design philosophy, since I don't believe that any launch vehicle has ever survived such an explosion, much less completed its mission to perfection.