Final answer:
The expansion of the Grande Armée was not a mistake made by Napoleon during his conquest of Europe; it actually contributed to his successes.
Step-by-step explanation:
The mistake that Napoleon did not make during his conquest of Europe is D. The rapid expansion of the Grande Armée. In fact, by 1812, Napoleon's Grande Armée was the largest armed force ever seen, boasting a total of a million soldiers.
This massive army was one of Napoleon's strengths and contributed to his many early successes during his European conquests. The other options listed, A. The invasion of Russia in 1812, B. The Continental System, and C. The Peninsular War in Spain, were all distinct mistakes that Napoleon made which ultimately led to the downfall of his Empire.