I think it’s a legit accident until proven otherwise. Piper Alpha in 1988 pretty much showed how intrinsically risky these operations are.
The examples I gave of "sneaky" blowouts -- Ixtoc and Santa Barbara -- had different causes and pathways, but you don't always get the warning pit-volume gains when you're losing control of a well. Underground blowout zone-to-zone behind pipe is an example; and Santa Barbara was a behind-pipe blowout that came to surface outside the casing strings.
Ixtoc blowout was gas-cut oil-base mud, sneaky, dangerous, and fast -- like this one! If BP was using water-base mud, then that scenario's off the table.