Spoilers follow for this week's issue of Infinity #1 from Marvel Comics.
As depicted in Infinity #1, The Builders come upon Galador where Ikon and the rest of the Spaceknights defend their planet; however, all is lost as a world bomb is unleashed blowing the planet to smithereens.
As Cosmic Book News M.E. Bryron Brewed stated in his Infinity #1 review, during Annihilators it was suggested that Rom the Spaceknight was off planet.
While we may never see Rom due to licensing issues, that doesn't mean that other Spaceknights weren't off planet as well.
And that's exactly what Jonathan Hickman says, as well as stating he blew up Galador just to show how powerful the big bads are.
Hickman also says he will be revisting the Spaceknights later down the road.
Following the prologue with Thanos and his army we move right into the main action which kicks off with the destruction of Galador. I imagine "Rom" and Space Knights fans are probably wondering, why Galador?
Hickman: Well there were a couple of reasons. Number one was that I wanted to include the Space Knights and I thought it was a really cool set piece. Then on top of that, is an answer that I don't really want to reveal, but I'm happy to. I have an idea kicking around in the back of my head that I think would be super cool coming out of "Infinity" that deals with the Space Knights that have lost their planet. We'll see the survivors of Galador later on in "Infinity."
So there are several reasons behind it, but probably the most honest and obvious answer is that we wanted to show what our bad guys were capable of.