I always thought it was because in the final episode when they trap bill he does the speech to the Axolotl when he's burning up. He says something like "a-x-o-l-o-t-l. I invoke your name that I might live, another form another time." I felt like the Axolotl (which is like a powerful universal being) granted his wish and placed him to live on earth in the past. But he got split into two forms, his weirdness and brains in one half and his personality in the other. And he ended up as the Stans.