This is BALONEY! Elon you are such a drama queen! Check your weld schedules and weld x-rays in the area of the explosion before you start with the drama. It looks like they unzipped the tank on the pad to me. Probably due to bad welds (expulsions or cryogenic cracking) or just a weak welding schedule to begin with. Do your proper Failure Analysis before you start shooting your mouth off.
Ditto. SpaceX have a so-so safety record. Their last one blew because of a faulty strut. And NASA and others ripped them a new one during the safety investigation for doing a piss poor investigation. Sabotage? Grow up Elon.
Yes. Construction fault becomes apparent during loading of fuel (or helium?) at high pressure.
Due diligence. It goes by the wayside too often.