Why did Britain and France not stop German rearmament in the 1930s?

Britain was overstretched policing its empire and could not afford major rearmament. Its main ally, France, was seriously weakened and, unlike in the First World War, Commonwealth support was not a certainty.

Explanation:

Simply because they were not truly prepared for war. This was because, in 1939, both France and Britain were massive colonial powers and were seen as the two most powerful countries in the world. France had the largest army in Europe while the British Navy was the most powerful naval force in the world.