So when they decided back in 1979 to remove instead of replace the faulty safety valve whose absence caused the leak, was no one aware that a leak could lead to

So when they decided back in 1979 to remove instead of replace the faulty safety valve whose absence caused the leak, was no one aware that a leak could lead to two weeks of blackouts in LA? Which is worse, that they knew and didn't replace the valve anyway, or that no one knew?