@teerack: Sorry for the late reply, but I just read this and could not agree more with your last sentence in the spoiler tag. While it could be interesting in the future, I am disturbed by the events that took place. It's worse than death if you ask me.
Galactus feeds on a planet's biospheric energy. Destroying the planet must disperse the energy so that it might take too much effort for him to collect or transform or reduce the energy so that he cannot use it .