For forty days the flood waters grew deeper… Everything that breathed and lived on dry land died. God wiped out every living thing on the earth and the birds of the sky. All were destroyed.

Genesis 7:17-23 NLT

Why would a loving God do such a thing?

First let’s take quick a look at the back story:
During the fall of Adam and Eve at the garden, God prophesied to the snake (Satan) that Eve’s offspring will crush his head (Genesis 3:15).

Now fast forward to Noah’s time, let’s take a look at the state of Eve’s offsprings:

There were giants on the earth in those days, and also afterward, when the sons of God came in to the daughters of men and they bore children to them. Those were the mighty men who were of old, men of renown.

Genesis 6:4 NKJV (emphasis mine)

The term ‘sons of God‘ in the Bible refers to beings that came directly from God. This includes the angels (see Job 1:6; 2:1) as well as Adam (see Luke 3:38), and Jesus as a man through virgin birth. In the New Testament, we have been adopted into God’s family as His sons and daughters through Jesus. But in this verse, ‘sons of God’ were the fallen angels who were cast down to earth along with Satan because of their rebellion against God (Revelation 12:4)

Hybrid offspring between the ‘gods’ and humankind? Half man, half ‘god’? Doesn’t this remind you of Greek mythology? Regardless whether there is some connection to it or not, the Bible clearly states the existence of these hybrid creatures.

The NLT Bible translation says that these hybrid creatures became the ‘heroes and famous warriors of ancient times’.

So during Noah’s time, the genes of the human race had been corrupted from fallen angels having sex with human beings. All except Noah’s family (Genesis 6:9-10)

The Bible goes on to say:

…every intent of the thoughts of their hearts was only evil continually.

Genesis 6:6

ALL their intents were evil continually. I don’t think I can fathom or imagine how the world looked like back then.

Corrupting the human race was Satan’s attempt to stop the promised seed from being born—the One who will ‘crush his head’ (Genesis 3:15).

You will see this theme throughout the Bible: Satan trying to stop the fulfillment of the promised seed—starting from Abel’s murder, then the corruption of the human race during Noah’s time, then the murder of babies during Moses’ time, and another infanticide during the time of Jesus’ birth. Throughout these events, he used human beings like the Pharaoh and Herod to execute his plan, thinking any of the victims could be the promised seed.

Here’s a line in Revelation:

And the dragon stood before the woman who was ready to give birth, to devour her Child as soon as it was born.

Revelation 12:4 NKJV

Clearly, Satan is not omniscient. He did not know God’s plan. He probably thought he had succeeded when Christ was crucified. No one—not even the Jews at that time—knew that it was a beautiful culmination of God’s love and justice without compromising one or the other. Christ’s death and resurrection was necessary to offer salvation for all. Only God’s wisdom can do that. Indeed, as prophesied, Satan crushed Jesus’ heel but Jesus crushed Satan’s head (with His resurrection and fulfilment of the New Covenant that offers salvation to ALL who believes Him).

So going back to the question – why did God flood the earth and wipe out everyone in it? It was His kindness and mercy to save the purity of the human race, to fulfill the birth of His promised seed for the salvation of all.

Why would God go through such extreme length to save humankind? The same answer can be applied to: Why did He choose to come in lowly human form, be scourged, spat on, mocked, and crucified and die a horrible death?

It’s because of God’s radical love for us.