Bab 1343: A Dangerous Hobby.

It was because of the trait of preparedness that he survived the first sage's scheme against him in the Unified Skill Index. And it is because of this preparedness that he planned for a way to divert the disaster that would have occurred to them had the plan failed. 

That contingency plan which is the same one they have in case CARNAGE escapes is to divert most of the calamity to the first sage. So even if the plan to use CARNAGE as fuel to kickstart their World Engine failed, they would have angered the first sage at most and had to limit their activities to the realm. That isn't much of a problem for them.

It is still a risky and dangerous plan that they executed only because of their trust in Soverick. If they can't trust themselves, who will they trust? If it were any other person who certified the plan and recommended it to them, they would have run away without turning back.