Well, it is important to recognize that the elephant in the room is: What if Germany had attacked the Soviet Union in the first place? Stalin probably had the project running for a decade...and that was the right answer for a paranoid man with no end to his enemies.
And the only man he ever trusted was Hitler, who proved to be the man to trust. Clearly, the way to get this to happen is to get Germany to Attack the Soviet Union, instead of the Soviet Union and Germany allying and divving up the UK.