The view of the Torah is that even though the slaves had yearned for freedom for so long, the Exodus came suddenly and “they were thrust out of Egypt and could not tarry” (ibid.).
The explanation of Dayan Isidor Grunfeld in his authoritative work, “The Jewish Dietary Laws”, is that “The Exodus was not a rebellion or a political plot of slaves prepared and planned a long time beforehand. It came suddenly and was manifestly a supernatural intervention of the Divine Redeemer. The redemption from Egypt was brought about by God alone. Our ancestors did nothing towards it. Indeed, their exodus was so little dependent upon their own power and foresight that they neither did not could prepare themselves with that most essential food, bread, for their awe-inspiring wanderings.”
We practical people are sure we would have handled the situation differently. We would have had a strategy all worked out, to be put into place the moment the opportunity arose. But it is not so easy when your fate depends on others. Opportunity knocks when it knocks. In the case of the Israelites, since it was God who promised they would not remain slaves for ever but would eventually become free, it was He who ensured they would not die from starvation. The success of the Exodus was in His hands, and He did not let the Israelites down.
Yet they were not entirely unprepared despite this. If they had come to terms with being slaves and accepted their fate without dreaming, yearning, hoping, praying for something better, they might have lost the right to be free. Their preparation was that their hope never died, and when hope never dies one knows that the redemption, however long delayed, must inevitably come.