Imagine it’s 1935....you have to choice to support one country against the other.
Country A: Desires colonies in the East, but makes no claim on any British colonies or interests.
Country B: A country whose stated goal, is working towards the violent overthrow, and physical extermination of the ruling class in every country in the world.
Without the benefit of hindsight, which one would you support?
Overall, I would imagine that the Brits were hoping that Hitler and Stalin would take each other out.