The earthquake didn't cause any damage. The single point of failure was the seawall being breached. The rest was a zipper of each failure causing the next. The tragedy is this zipper could have been halted at many places.

For example, the hydgrogen overpressure in the reactor (caused by previous failures) was vented through an overpressure valve into a pipe. The pipe exited into the enclosed reactor building, which lead to an explosion.

The pipe should have been vented to the exterior. The cost of that would have been insignificant, like numerous other zipper-stops.

Deepwater Horizon was a big zipper, too, none of which would have been costly to prevent.