And the lean and the ill favored kine did eat up the first seven fat kine:

Matthew Henry's Concise Commentary

41:9-32 God's time for the enlargement of his people is the fittest time. If the chief butler had got Joseph to be released from prison, it is probable he would have gone back to the land of the Hebrews. Then he had neither been so blessed himself, nor such a blessing to his family, as afterwards he proved. Joseph, when introduced to Pharaoh, gives honour to God. Pharaoh had dreamed that he stood upon the bank of the river Nile, and saw the kine, both the fat ones, and the lean ones, come out of the river. Egypt has no rain, but the plenty of the year depends upon the overflowing of the river Nile. See how many ways Providence has of dispensing its gifts; yet our dependence is still the same upon the First Cause, who makes every creature what it is to us, be it rain or river. See to what changes the comforts of this life are subject. We cannot be sure that to-morrow shall be as this day, or next year as this. We must learn how to want, as well as how to abound. Mark the goodness of God in sending the seven years of plenty before those of famine, that provision might be made. The produce of the earth is sometimes more, and sometimes less; yet, take one with another, he that gathers much, has nothing over; and he that gathers little, has no lack, Ex 16:18. And see the perishing nature of our worldly enjoyments. The great harvests of the years of plenty were quite lost, and swallowed up in the years of famine; and that which seemed very much, yet did but just serve to keep the people alive. There is bread which lasts to eternal life, which it is worth while to labour for. They that make the things of this world their good things, will find little pleasure in remembering that they have received them.