In Eyvinds Defense: Nobody of the Chieftains may listen to him. He did actually ask both chieftain about the proof at least.
In Axel Defense: 1. Unlike Nauxus he never saw the Culprit. 2. The Lizards already invaded Territory by establishing hidden outposts and declared war. Axel also knows that his Tribe is at a strategic disadvantage. His Priority is to keep his Tribe safe and win this War or face extinction.