Because it showed that God was keeping his promise (Genesis 15:13-14) to Abraham, and it showed that God can change the laws of nature at will.
It symbolizes the beginning of The Passover.
The exodus from Egypt
because moses let his people out of Egypt
From a historical perspective, the single most important event in Jewish history was the Babylonian Exile, but this, and the return from Exile, are not really an 'Exodus'.The story of the Exodus from Egypt was important in Jewish biblical tradition, but not in history. Nearly all scholars say there was no Exodus from Egypt as described in The Bible, so the Exodus could not be important in a normal historical sense.
Egypt. And you're wrong. The most important event was the Giving of the Torah at Mount Sinai, not the Exodus.
The Exodus
The Torah calls the flight from Egypt the Exodus, Which means "departure." It became a central event in the history of the Hebrew people.
One example would be the Exodus from Egypt; another is the Giving of the Torah.
The answer that you're looking for is "Judaism," but it is not entirely correct. The Exodus from Egypt was of vast importance in Judaism but was just a prelude to God's Giving of the Torah at Mount Sinai.
The Hebrew people sprayed blood on the door of their houses in Egypt, and the angel passed by these houses. and the first born escaped. But the egyptians did not have it on their doors so their first born was slain.
The event is known as the "Exodus" in English and the "Yetsiat mi-Miztrayim" (יציאת מצרים) in Hebrew.
It was when they stopped being slaves and gained the self-responsibility that comes with freedom. It marked the Israelites' transition from a family into a nation; and it was the prologue to the Giving of the Torah.