After all that had been brought upon him (see The Defeat Of Pharaoh's Magicians, Plagues Of The Pharaohs: Past and Future, Let My People Go and The LORD Of Passover), the Pharaoh had enough, for a while (he would pursue them after their departure, but that would only result in greater damage to him when his army was drowned in the sea):
"12:29 And it came to pass, that at midnight the LORD smote all the firstborn in the land of Egypt, from the firstborn of Pharaoh that sat on his throne unto the firstborn of the captive that was in the dungeon; and all the firstborn of cattle. 12:30 And Pharaoh rose up in the night, he, and all his servants, and all the Egyptians; and there was a great cry in Egypt; for there was not a house where there was not one dead [see What Happens When You Die?].
"It shall be for a sign ... and for a memorial ... that the Lord's Law may be in thy mouth: for with a strong hand hath the LORD brought thee out of Egypt"
The Egyptian people too were eager for the Exodus to happen - they had been suffering the plagues because of their leader's arrogance:
"12:33 And the Egyptians were urgent upon the people, that they might send them out of the land in haste; for they said, We be all dead men. 12:34 And the people took their dough before it was leavened, their kneadingtroughs being bound up in their clothes upon their shoulders. 12:35 And the children of Israel did according to the word of Moses [see The Master's Messenger]; and they borrowed of the Egyptians jewels of silver, and jewels of gold, and raiment: 12:36 And the LORD gave the people favour in the sight of the Egyptians, so that they lent unto them such things as they required. And they spoiled the Egyptians." (Exodus 12:33-36 KJV)
"12:37 And the children of Israel journeyed from Rameses to Succoth, about six hundred thousand on foot that were men, beside children. 12:38 And a mixed multitude went up also with them; and flocks, and herds, even very much cattle. 12:39 And they baked unleavened cakes of the dough which they brought forth out of Egypt, for it was not leavened; because they were thrust out of Egypt, and could not tarry, neither had they prepared for themselves any victual." (Exodus 12:37-39 KJV)
The deliverance happened exactly as the LORD had promised to Abraham in The Exodus Prophecy centuries before.
"12:40 Now the sojourning of the children of Israel, who dwelt in Egypt, was four hundred and thirty years. 12:41 And it came to pass at the end of the four hundred and thirty years, even the selfsame day it came to pass, that all the hosts of the LORD went out from the land of Egypt. 12:42 It is a night to be much observed unto the LORD for bringing them out from the land of Egypt: this is that night of the LORD to be observed of all the children of Israel in their generations." (Exodus 12:40-42 KJV)
The Passover (see The True Christian Holy Days: Lesson 1) represented the sacrifice for sin, while the Days of Unleavened Bread (see The True Christian Holy Days: Lesson 2) represented the acceptance of the Passover sacrifice by obeying the LORD i.e. "13:9 And it shall be for a sign unto thee upon thine hand, and for a memorial between thine eyes, that the Lord's law may be in thy mouth: for with a strong hand hath the LORD brought thee out of Egypt" (Exodus 13:9 KJV). That observance is the basis of Christianity i.e. Christ died for repentant sinners; unrepentant sinners will be cast into the lake of fire.
"13:3 And Moses said unto the people, Remember this day, in which ye came out from Egypt, out of the house of bondage; for by strength of hand the LORD brought you out from this place: there shall no leavened bread be eaten. 13:4 This day came ye out in the month Abib [see Bible Calendar and Bible Months]. 13:5 And it shall be when the LORD shall bring thee into the land of the Canaanites, and the Hittites, and the Amorites, and the Hivites, and the Jebusites, which he sware unto thy fathers to give thee, a land flowing with milk and honey, that thou shalt keep this service in this month.
Fact Finder: (a) The people of Israel were set free with the Exodus. But what happened to them when they foolishly used their freedom for lawlessness i.e. Violence? What happened when the Israelites did not accept the Sacrifice of the LORD by obeying Him? (b) How do many Christian-professing people today make the same mistake as the Israelites who came out of Egypt?