Odin is skilled in the art of psychological warfare. The way he treated the Jotnar is a perfect example of this (and so was Bor before him, with the Dark Elves). Imperialism 101: colonize your less industrialized victims after winning a war against them. School your children in their “innate inferiority” and skew your culture to be dominant over theirs, a symbol of your “enlightenment.” Play the “benevolent parent” (how convenient the traditional Norse mythological title of “Allfather” becomes) over them, implicitly rendering them the monstrous and ungrateful enemy should they revolt. Leave them economically dependent on you as well. Make your “peace treaty” nominal only.