Isaiah authorship

One of the more troubling aspects of higher criticism was the dates of the book of Isaiah, which may have had two or three authors. In short, the writings hadn't been written before Lehi left for the Americas.

Here's a defense offered by a writer at the Maxwell Institute: He says, channeling BH Roberts, such critics show the "unwillingness of modern scholars to accept the possibility of miracles, including foreknowledge of the future by prophets."

To me, this is a tacit admission that there probably were multiple writers of Isaiah, and the dates are problematic for the BOM, so the answer must be that Lehi or Nephi were given them before the fact by an act of God.

This does not strike me as a satisfactory answer. Miracles can be used to explain away anything. It's seen as a trump card when I view it as fallacious. Which Isaiah was Jesus referring to, then, when he said "Great are the words of Isaiah?" And why didn't Nephi tell us those sections were obtained via a miracle?

Or maybe the answer is because the BOM was written by Joseph Smith and this is one of several anachronistic elements.