“And it came to pass in the course of those many days that the king of Egypt died; and the children of Israel sighed by reason of the bondage, and they cried, and their cry came up unto God by reason of the bondage. And God heard their groaning” (Exodus 2:23-4). This means that they suffered so much that they could not bear it any longer. And they so pleaded with prayer, that “their cry came up unto God.”
But we can see that they were saying, “Would that we had… when we sat by the flesh-pots, when we did eat bread to the full.” And they also said, “We remember the fish, which we were wont to eat in Egypt for naught; the cucumbers, and the melons, and the leeks, and the onions, and the garlic.”
The thing is that, indeed, they were very fond of the work in Egypt. This is the meaning of “But mingled themselves with the nations, and learned their works.” It means that if Israel are under the dominion of a certain nation, that nation controls them and they cannot retire from their dominion. Thus, they tasted sufficient flavor in that work and could not be redeemed.
So what did the Creator do? “The king of Egypt died,” meaning they had lost this servitude. Thus they could no longer work; they understood that if there is no perfection of the Mochin, the servitude is also incomplete. Hence, “and the children of Israel sighed by reason of the bondage.” The work means that they did not suffice for the work, that they had no liveliness in the work.
This is the meaning of “the king of Egypt died,” that all the dominations of the king of Egypt, which he was providing for and nourishing, had died. This is why they had room for prayer. And they were immediately salvaged. And afterwards, when they walked in the desert and came to a state of Katnut (smallness), they craved the servitude that they had had prior to the death of the king of Egypt.