Regardless of the reason, the decision to let up allowed the British to gather as many boats as possible, resulting in 340,000 troops fleeing to the UK in one of the largest evacuations of all time.
The reasoning behind this decision is still unclear to historians. Some speculate it was due to Hitler's belief that the Allied forces were essentially already defeated. Others assert it was to give the German Army some rest, as their advances had been so rapid up to this point. Near the end of the war, Hitler himself claimed that he was allowing time for British Prime Minister Winston Churchill to make a deal with Germany. However, given the self-serving nature of such a statement and Hitler's record of not respecting peace agreements, this justification does not hold much water. Regardless of the reason, the decision to let up allowed the British to gather as many boats as possible, resulting in 340,000 troops fleeing to the UK in one of the largest evacuations of all time. Hence, despite a massive military defeat, with France ultimately falling, British propaganda portrayed the evacuation of Dunkirk as a victory.