What was the world like at the time of Peter's writing?
From Wiki -
"The author of these epistles writes of his addressees undergoing “various trials” (
1 Peter 1:6), being “tested by fire” (
1:7), maligned “as evildoers” (
2:12) and suffering “for doing good” (
3:17)"
...so the "New Heaven/New Earth" (which is the umbrella that the New Covenant is under - IOW....it's only a part of the "New Heaven/New Earth" ) had not been entirely fulfilled at that time...as I'm understanding (not until the destruction of Jerusalem/The temple). The destruction of Jerusalem/the temple has major significance.....that's what marked the "end of the world". It was the end of the
Jewish temple world.....not the end of our soil....our universe.
That's how Kingdom theology.....or "already not yet" theology works - there's a gradual progression in change. It's believed God's kingdom has been "inaugurated" but not yet "consummated".
Article on "Kingdom theology" (if interested) ~
https://www.samstorms.com/all-articles/post/the-kingdom-of-god:-already-but-not-yet---part-i
From that article linked above:
N.B. - In his response to John's disciples, Jesus was claiming that the fulfillment of the OT hope with its attendant blessings was in fact present in his person and ministry. The fulfillment, however, was not taking place along expected lines, hence John’s perplexity. The unexpected element was that fulfillment was taking place in Jesus, but without the eschatological consummation. The OT prophetic hope of the coming Messianic kingdom of God as promised to Israel is being fulfilled in the person and ministry of Jesus, but not consummated. The Jews of our Lord’s day, in keeping with what they saw in the OT, expected the consummation of the kingdom, the complete and final overthrow of Israel’s political enemies and the ushering in of the age of blessed peace and prosperity in the land. Our Lord, however, came with the message that before the kingdom would come in its eschatological consummation it has come in his own person and work in spirit and power. The kingdom, therefore, is both the present spiritual reign of God and the future realm over which He will rule in power and glory.