After a "god" visited Shardybarn and started religion on the planet, all the inhabitants believed that their god would literally save them from extinction as he promised. The inhabitants of Shardybarn placed many nuclear missiles within their planet in an attempt to summon their god back to save them.
Charlton Mackerel and the Eighth Doctor arrived on Shardybarn to try to stop the inhabitants from destroying their world. The inhabitants of the planet did not believe their claims of knowing the future and let the bomb detonate, which destroyed Shardybarn. (PROSE: The Tomorrow Windows)