If it was sabotage then a relatively small charge in the right place would do it. Sabotage to the BOP would of required a lot of preplanning and a team to execute. This smells like a simple case of doing the wrong thing at the wrong time with several back up systems failing all a once - likely? No. Possible? Yes.
If it’s so damned easy why doesn’t it happen all the time? When is the last time one blew up?
Ditto. Remember about 10 years back in NJ after a strange severely cold winter (with ten snow storms), an underground natural gas line cracked, leaked and exploded near my old man’s development 300AM in the morning. The entire sky was glowing red at night as the gas line burned before someone in the gas pipeline company finally shut the gas off. The burning fireball was so intense that it melted the paint on cars and shattered its windshields. The apartment complex next to the gas line had to be evacuated and luckily no one got hurt except for one heart attack.