The answer was simple: Brutrumukk's recently acquired gnome brain told him to do it. He wasn't entirely sure why it was telling him to do all of this, but it was insisting that if he did, the problem he and Jub now faced could be resolved without violence. This would in turn allow them to conserve energy for violence against the giant cats when they caught up to them.
Brutrumukk: You know, Jub, sometimes violence isn't the answer.
Jub: Wait, what?
Brutrumukk: Sometimes it's a question.
Brutrumukk: And the answer is...
Brutrumukk: ...
Jub: ...?
Brutrumukk: Maybe later.