1So Israel set out with all that he had, and came to Beersheba, and offered sacrifices to the God of his father Isaac.
2God spoke to Israel in visions of the night and said, "Jacob, Jacob." And he said, "Here I am."
3He said, "I am God, the God of your father; do not be afraid to go down to Egypt, for I will make you a great nation there.
4"I will go down with you to Egypt, and I will also surely bring you up again; and Joseph will close your eyes."
5Then Jacob arose from Beersheba; and the sons of Israel carried their father Jacob and their little ones and their wives in the wagons which Pharaoh had sent to carry him.
6They took their livestock and their property, which they had acquired in the land of Canaan, and came to Egypt, Jacob and all his descendants with him:
7his sons and his grandsons with him, his daughters and his granddaughters, and all his descendants he brought with him to Egypt.
If I understand this correctly, God caused or allowed a famine in the promised land and sent Joseph ahead to prepare a place for the family to survive and even multiply in Egypt. God, Himself, spoke to the old and fearful Jacob to reassure him that he should take his family to Egypt and renewed the promise to make a great nation of them there. God had plans for this special family from the foundation of the earth, a plan to bring about the salvation of mankind through them. It was not because they were particularly strong or godly, but simply because God picked them out and worked out His plan through them. They became the means through which God funneled His love for all of mankind.