[user104658]

Getting rid of Osborne is symbollic and probably necessary. He goes hand in hand with Cameron, unfortunately for him. They want to at least create the illusion of a "clean slate" Tory government, wash their hands of everything that came before and during the referrendum, both for the benefit of the GBP and to be able to say "You're dealing with this NEW government now" when trying to reforge international relationships.

Osborne being there in any capacity would firmly anchor them in the Tory-LibDem 2010+ era. He had to go.