There is a conspiracy theory that it is all Cameron's doing. I don't believe it but it goes like this.
Osborne's only qualification for being Shadow Chancellor is that he was in the same class at school as Cameron. However, his performance lately has been woefully poor and there are
many Conservatives calling for him to be replaced.
Problem is that Cameron is so close to Osborne on a personal basis, he finds it hard to sack his friend. What he needs is for Osborne to go of his own accord (to resign). Another close friend of Cameron,
Rothchild, has now put in motion events that could see Osborne having to resign, and the Conservative's having to appoint someone who knows what he is doing. Rothchild is a natural Tory who would put the party (and a Tory election victory) ahead of a personal friendship.