If the "end" Peter spoke of never came, his words would lose their urgency, credibility, and prophetic authority. Here's why:

It would make Peter a false witness, claiming "the end of all things is at hand" when it really wasn't (1 Peter 4:7).

It would conflict with Jesus' time statements, like "this generation will not pass away" (Matthew 24:34), since Peter echoed the same imminent expectation.

It would undermine the entire New Testament urgency, where the apostles constantly warned of a near judgment (James 5:8-9, Hebrews 10:25, 37).

It would make first-century exhortations meaningless for their audience if the "end" was 2,000+ years away.

It would challenge God's integrity, because the Spirit led Peter to write it.

But the fulfilled view shows Peter's words did have meaning, he was warning them of the approaching end of the Old Covenant world, which culminated in 70 AD. The "end" came, just as promised.