They don't give any damn about this. People can be living in a pod or whatever for them to do their goals on a desolate planet, with whatever remains.
The enemy is like a tick, that fundamentally has no care if they kill an animal or not, as they cannot see that far. All they care is to drain blood and in their case, destroy.
The other aspects of their "plan" won't be handled by those that they have here doing their errands, but from them. And the enemy certainly doesn't care if all life on the planet is gone aside a few slaves or something similar.
The enemy is like a tick, that fundamentally has no care if they kill an animal or not, as they cannot see that far. All they care is to drain blood and in their case, destroy.
The other aspects of their "plan" won't be handled by those that they have here doing their errands, but from them. And the enemy certainly doesn't care if all life on the planet is gone aside a few slaves or something similar.