It seems to be that the reason that the king of Egypt wanted to kill all the children of Israel is very clear; they were too many of them, he didn't want them to be the fifth column, he was afraid that they will reproduce and he will not able to control them.
This is what the bible share with us.
What is needed to be telling is another legend. Pharaoh slept in his house, in his dream he saw an old man with scales. In one side of the scales were all the Egyptian from the small to the big one; in the other side of the scales was only small lamb. The lamb determined all the side with the Egyptian people and pharaoh was so scared from this dream.
After he called to his sages and told them the dream they said to the king: the lamb is a sign to the leader from the people of Israel, those who are your servants. He will come from them and will take them out from Egypt with great force....
This is the reason why in the book of exodus 1:22 written:
"וַיְצַו פַּרְעֹה, לְכָל-עַמּוֹ לֵאמֹר: כָּל-הַבֵּן הַיִּלּוֹד, הַיְאֹרָה תַּשְׁלִיכֻהוּ, וְכָל-הַבַּת, תְּחַיּוּן"
"And Pharaoh charged all his people, saying: 'Every son that is born ye shall cast into the river, and every daughter ye shall save alive."
Pharaoh didn't want the lamb to be a shepherd!
Main phrases of the post + transcription + translation
Hebrew Transcription Translation
רוֹעֶה Rô'eh Shepherd
בְּיָד חֲזָקָה Beyād hăzaqa Forcefully
טָלֶה Tāleh Lamb
מֹאזְנַיִם mōznayim Scales
גַּיִס חֲמִישִׁי Gayis hămîšî Fifth column