Read the article. It says:

But there’s no doubt that a pool containing many tons of highly radioactive used fuel is suspended 100 feet in the air, with little left to support the structure. Should an earthquake or other trauma knock the pool to the ground, there’s a high likelihood the fuel rods could catch fire.

In such an event, the radioactive emissions could be catastrophic. Intensely lethal emissions could spew for a very long time, eventually circling the globe many times, wrecking untold havoc.