The accident described as unforeseeable may have been predicted by someone whose warning was inconvenient.

Unforeseeable often means unwelcome. Someone frequently did see it, said so, and was overruled because acting on the warning would have cost time or money, and afterwards the event gets described as impossible to anticipate. The word does a lot of work in protecting the decision that was made.

When you hear that nobody could have known, it is worth asking whether anyone did. And in your own organisation, notice what happens to people who raise inconvenient possibilities. If they get quietly sidelined, you will end up with a lot of unforeseeable events, all of which were foreseen by someone who learned not to say so twice.