Here's something else to consider about the "world that then was" of 2 Pet.3, pointing to why God brought a destruction upon the old earth with a flood of waters to end Satan's original rebellion of old, at some point in between Gen.1:1 and Gen.1:2.
Rev 12:3-4
3 And there appeared another wonder in heaven; and behold a great red dragon, having seven heads and ten horns, and seven crowns upon his heads.
4 And his tail drew the third part of the stars of heaven, and did cast them to the earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.
KJV
Per Rev.12:9, that "dragon" is simply another title for Satan.
Those phrases above in bold represent the time of Satan's original rebellion against God. That's when Satan drew a third of the angels ("stars") to earth with him in rebellion.
Do you notice within that same timing we are shown Satan did that rebellion of old with a system having "seven heads, and ten horns, and seven crowns"?
That is not about his future system of today that's to have ten crowns per Rev.13:1. That one of old that had only seven crowns involved his exalting himself with that old beast kingdom he first rebelled with, a third of the sons of God in rebellion with him.
That time is about this parable God gave in Ezek.31 using the Assyrian to point to him metaphorically in that time of old when Satan was exalted, and then rebelled against God. There's a similar parable in Ezek.28 about him in that time also:
Ezek 31:3-9
3 Behold, the Assyrian was a cedar in Lebanon with fair branches, and with a shadowing shroud, and of an high stature; and his top was among the thick boughs.
4 The waters made him great, the deep set him up on high with her rivers running round about his plants, and sent out her little rivers unto all the trees of the field.
5 Therefore his height was exalted above all the trees of the field, and his boughs were multiplied, and his branches became long because of the multitude of waters, when he shot forth.
6 All the fowls of heaven made their nests in his boughs, and under his branches did all the beasts of the field bring forth their young, and under his shadow dwelt all great nations.
7 Thus was he fair in his greatness, in the length of his branches: for his root was by great waters.
8 The cedars in the garden of God could not hide him: the fir trees were not like his boughs, and the chestnut trees were not like his branches; nor any tree in the garden of God was like unto him in his beauty.
9 I have made him fair by the multitude of his branches: so that all the trees of Eden, that were in the garden of God, envied him.
KJV
Although God gave that as a message to Pharaoh, and using the Assyrian, we know neither of those were in God's Garden of Eden. But Satan once was.
In Ezek.31:6, God temporarily leaves His parable of using the high cedar and trees in His Garden to symbolize Satan's high status in that time before he rebelled, and then tells us directly, "and under his shadow dwelt all great nations". Why did God leave those symbols with that statement about nations dwelling under his shadow? and then right after that continue with His metaphor of the high cedar and trees in His Garden of Eden? When our Heavenly Father does something like that in His Word, it means He's showing us something we need to consider more deeply.
Our Lord Jesus revealed that point again right there in Rev.12:3-4 about the system of old that Satan as that "red dragon" of old rebelled against God with, drawing a third of the angels into rebellion with him. That means the idea of 'nations'... literally existed in that time old when Satan first rebelled. And it has mean about the sons of God in that time of those nations, not flesh man, for Adam had not yet been created then when Satan first rebelled with that original system of seven heads, ten horns, but only seven crowns.
How many have also missed this in Isaiah 14, where God is giving a proverb (or parable) about Satan again:
Isa 14:7-12
7 The whole earth is at rest, and is quiet: they break forth into singing.
8 Yea, the fir trees rejoice at thee, and the cedars of Lebanon, saying, "Since thou art laid down, no feller is come up against us."
9 Hell from beneath is moved for thee to meet thee at thy coming: it stirreth up the dead for thee, even all the chief ones of the earth; it hath raised up from their thrones all the kings of the nations.
10 All they shall speak and say unto thee, "Art thou also become weak as we? art thou become like unto us?"
11 Thy pomp is brought down to the grave, and the noise of thy viols: the worm is spread under thee, and the worms cover thee.
12 How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations!
KJV
There's that cedar metaphor again with the trees speaking about Satan in verse 8. It's easy to just pass this off and say all that is given about Satan's eventual casting into his pit prison of Rev.20, which it is about that. But our Heavenly Father didn't just use that cedar and trees analogy again here to point to this present world. It's pointing to the parable He gave in Ezekiel 31 about Satan's original status in His Garden also. And I believe that 'nations' pointer is included also.