>>12765505oversimplification. Most of it has to do with the position of the continents.
1. Antarctica's position on the south pole.
2. Australia broke off from Antarctica allowing the creation of the Antarctic Circumpolar Current which prevents warm water from reaching the continent
3. The merging of North and South America at the Isthmus of Panama preventing warm water from circulating from the Pacific to Atlantic oceans and diverting it instead toward the poles where it cools quickly because of the Atlantic and Pacific gyres.