I don't think the FAA cares about the explosion itself. They care about the safety of flights and the safety of people on the ground as far as flying things falling on them.
My best guess is that SpaceX did last minute changes to the rocket, either hardware or software, deviating from the documents submitted to the FAA. This could explain why the FAA only reacts now and would make sense with what Musk said about the procedures not being able to cope with the pace of development they have.
what I have been hearing is that the violation is in regards to a flight termination system not activating. SN8 crashed due to the header tank not having the required pressure to relight the engine. They posted that info really quick, so.. did they know during descent, prior to the landing attempt that it didn't have pressure, or prior to landing-flip? If so, wouldn't a rocket hurtling towards the ground with no chance of landing properly require a flight termination? I can't validate this, just what i've heard from insiders, but the violation was confirmed to involve the "explosive landing" so that info seems to go that way. It would make sense that they delayed termination to see if the landing flip was successful, or to at least show it, since that is the main maneuver that makes starship such a different rocket.
