Arizal reveals that the Jews in Egypt had sunken to level 49 of impurity. They had to be redeemed in great haste to catch them before they slipped to level 50, which would have deemed them irredeemable.

What was the purpose of this?

Yetzias Mitzrayim was the root of all future redemptions.

Hashem wanted us to be redeemed from the lowest possible point in order to create an everlasting ability for a Jew to be redeemed from anywhere.

No Jew can say today that he has slipped to the point of being irredeemable. Hashem redeemed us from level 49 out of Egypt and we can access that point of freedom wherever we find ourselves today.