Why did a goat eat the "unchanged Quran" & why didn't Allah stop the goat?

No one in their right mind would believe in those specific "hadiths" even if they really are in hadith books. Not all hadiths are genuine - not especially if they contradict the Qur'an. Those contradict the glorious Qur'an, astaghferullah, thus it is obvious they are fabrications. No one is going to put what was collected and written by men over what came from Allah subhana wa ta'ala anyhow, insha'allah.