All US boosters (I assume other nations as well) have flight termination systems. The goal is to try and stop an out of control booster (Big vehicle, full of explosives/fuel/oxidizer) from causing MORE harm.
When the CRS-16 mission booster (Core B1050) clearly was spinning out of control on landing, why did they not use the FTS to blow it, instead of letting it try to land.
That is actually was pointed somewhere safe (would divert if all was going well to land, by design) and that it actually landed softly on the water, is sort of immaterial.
Why did the flight safety officer not terminate the flight?