Now that I have laid out the major themes and emphases of 1 Peter in my previous post, I can move on to the questions of who wrote it, when, and why. The final issue in some ways is easiest, at least when it comes to the overarching purpose of the letter. As we have seen, the author is concerned about Christians’ reactions to their persecutions, and is intent that they give their opponents no grounds for opposition but lead upright lives, being a “witness” to those who challenge their faith, and imitating Christ in suffering unjustly. Whoever wrote the letter, and when, it seems reasonably safe to assume this was the major reason for it. We will see later, however, that there may be at least one less obvious reason as well.
For the issues of who wrote it and when, I provide here is largely based on my more extended study, Forged… Why The Bible’s Authors Are Not Who We Think They Are (HarperOne).

Bart wrote: “by “write” I mean that most people – even if they could copy down words — could not compose a sentence,”
But if someone could speak a sentence in his native language and could copy down words, would he not then be able to copy down the sentence he just said? In this letter, “Peter” seems to just be a guy telling his friends to be careful what they do. Not a lot of composition required.
You would think. But often the answer is no. (I’ve even have PhD students who are highly articulate orally, but cannot compose a really good paragraph to save their soul.) And if the answer is yes, the people who speak but can’t compose would not be able to construct highly rhetorical phrasing in a different language. There are millions of immigrants in the US who are not well educated but can function in English well enough to get by. I’ve never met any who could write a compelling short story (in English). Some of them are crazy smart and far better than me at other things — but you can’t compose literature without training and do it in another language without *extensive* training.