Craig's civilization has full control over matter, but they still cannot violate basic thermodynamics: they can't create new energy or matter. But they can very easily control what happens to all the matter they have.
As a result, the whole Andromeda galaxy is basically dark — the whole thing only has a few dozen stars, down from about a trillion.
A human is asking Craig why this is so, and Craig replies:
Say you found yourself on a farm, just at the start of what promises to be a long, brutal winter.
In your yard there are several hundred bundles of firewood. Each bundle is enormous. Your family only needs one bundle to get itself through the winter.
One night, there's a huge lightning storm. The bundles are the only tall thing on the plain; most of them get struck and catch on fire. Do you let them burn?
What if they're pretty? Do you let them burn, then?
What if there are insects keeping warm by these fires? If you mean to put out the fires, do you carefully evacuate each one to your own hearth, first?
The human narrowed his eyes. He knew what humans would do. And he knew who the insects were, here.
The questions were rhetorical, but he didn't know their answers. He just hoped that the aliens were better than we are.