>>57631466As real species, specialization makes them fragile compared to highly adaptable species, such as smilodons and wolves. One specialized in giant prey with little tolerance for its peers and a fixed territory, while the others opted for group strength, extensive territories, and a broader diet of small and medium-sized prey, carrion, and sometimes even fruit.
Another explanation is that it happened like the encounter between Neanderthals and Homo sapiens. There are several theories, ranging from extermination due to habitat competition, assimilation through reproduction, or the possibility that humans carried pathogens that Neanderthal antibodies couldn't combat.
In this case, the southern Sneasel and Weavile migrated and competed for resources and territory, individually being weak against a Sneasler but superior as a group.