Rabbi Noson Weisz writes in this article on Aish.com:

A LESSON OF THE HOLOCAUST

As we know from the Holocaust, the memory and impact of extraordinary historical incidents fades rapidly indeed. Because the Holocaust was such an impossibly unlikely event, some people find it difficult to give it credence a short half century after it was concluded, and this in spite of the extensive records and even pictures available. If this is true of the Holocaust how much more does this apply to the Exodus. The Exodus lives on only in the mitzvot that commemorate it.