“Does he speak and then not act? Does he promise and not fulfill?”

Why did God allow the famine to worsen to the point of affecting the land of Canaan even more severely,

prompting Jacob to go down to Egypt and eventually making his descendants into a great nation there 

(Genesis 43:1; 46:3)? Why didn't God, like with Jacob's father Isaac (26:2-4),

just let Jacob stay in the land of Canaan and make his descendants into a great nation there?

When reflecting on these words, I recall the incident when Jacob's mother Rebekah

urged him to flee to her brother's house in Haran (27:43-44).

During his twenty years there, Jacob took two wives and two concubines,

and he fathered eleven sons and one daughter (29:30).

When God prospered Jacob in Haran and eventually led him back to his homeland and relatives,

He said, "I will surely make you prosper and will make your descendants like the sand of the sea,

which cannot be counted" (32:9, 12). In fulfilling this promise, God caused Jacob

to bring his entire family down to Egypt, which consisted of a total of seventy people (46:27).

Yet, as God had promised to Abraham, He made Jacob's descendants endure slavery

and oppression in Egypt for four hundred years (15:13),

eventually making them a nation of over six hundred thousand (Numbers 11:21).

This brings to mind the words of Numbers 23:19:

"God is not human, that he should lie, not a human being, that he should change his mind.

Does he speak and then not act?  Does he promise and not fulfill?"