So he let the wickedness manifest, just to kill them and infants in the end?
Abraham had the same problem in Genesis 18
16 When the men got up to leave, they looked down toward Sodom, and Abraham walked along with them to see them on their way. 17 Then the Lord said, “Shall I hide from Abraham what I am about to do? 18 Abraham will surely become a great and powerful nation, and all nations on earth will be blessed through him.[
a] 19 For I have chosen him, so that he will direct his children and his household after him to keep the way of the Lord by doing what is right and just, so that the Lord will bring about for Abraham what he has promised him.”
20 Then the Lord said, “The outcry against Sodom and Gomorrah is so great and their sin so grievous 21 that I will go down and see if what they have done is as bad as the outcry that has reached me. If not, I will know.”
22 The men turned away and went toward Sodom, but Abraham remained standing before the Lord.[
b] 23 Then Abraham approached him and said: “Will you sweep away the righteous with the wicked? 24 What if there are fifty righteous people in the city? Will you really sweep it away and not spare[
c] the place for the sake of the fifty righteous people in it? 25 Far be it from you to do such a thing—to kill the righteous with the wicked, treating the righteous and the wicked alike. Far be it from you! Will not the Judge of all the earth do right?”
26 The Lord said, “If I find fifty righteous people in the city of Sodom, I will spare the whole place for their sake.”
27 Then Abraham spoke up again: “Now that I have been so bold as to speak to the Lord, though I am nothing but dust and ashes, 28 what if the number of the righteous is five less than fifty? Will you destroy the whole city for lack of five people?”
“If I find forty-five there,” he said, “I will not destroy it.”
29 Once again he spoke to him, “What if only forty are found there?”
He said, “For the sake of forty, I will not do it.”
30 Then he said, “May the Lord not be angry, but let me speak. What if only thirty can be found there?”
He answered, “I will not do it if I find thirty there.”
31 Abraham said, “Now that I have been so bold as to speak to the Lord, what if only twenty can be found there?”
He said, “For the sake of twenty, I will not destroy it.”
32 Then he said, “May the Lord not be angry, but let me speak just once more. What if only ten can be found there?”
He answered, “For the sake of ten, I will not destroy it.”
33 When the Lord had finished speaking with Abraham, he left, and Abraham returned home.
Moses even had the same problem in Exodus
11 Then Moses pleaded with [
a]the Lord his God, and said: “Lord, why does Your wrath burn hot against Your people whom You have brought out of the land of Egypt with great power and with a mighty hand? 12 Why should the Egyptians speak, and say, ‘He brought them out to harm them, to kill them in the mountains, and to consume them from the face of the earth’? Turn from Your fierce wrath, and relent from this harm to Your people. 13 Remember Abraham, Isaac, and Israel, Your servants, to whom You swore by Your own self, and said to them, ‘I will multiply your descendants as the stars of heaven; and all this land that I have spoken of I give to your descendants, and they shall inherit
it forever.’ ” 14 So the Lord relented from the harm which He said He would do to His people.
Although God relented from destroying them in this example in the short term, he made them walk around in the wilderness till they all died off in the long term, and then entered the Promised land.
Both holy men struggled with God to try and save lives. In fact, the world Israel means to struggle with God.
However, in both examples God was struggling with man to eradicate the sin and not the people.