The main reason for doubt of the letter 2 Peter is because it seems so different from 1 Peter. I have argued elsewhere that 1 Peter was composed largely by Silvanus (Silas) the prophet (see Acts 15.32). Peter indicates that he wrote (or authorized) the words of 1 Peter in 1 Pet. 5.12: By Silvanus, a faithful brother as I regard him, I have written briefly to you, exhorting and declaring that this is the true grace of God. Stand firm in it (ESV). The ESV is superior to the NIV here as it reflects the Greek clause “dia Silvanus” without reading into the text by adding the word “help.” Sure, Silvanus “helped,” but how much, nobody knows. The text says “by (or, through) Silvanus which seems to indicate, or could imply substantial authorial composition with Peter’s agreement and approval.

How 2 Peter Made It into the Bible