"of worth unto my brethren"

The first verse of Moroni relates something important if we have eyes to read and minds to think.

4 Wherefore, I write a few more things, contrary to that which I had supposed; for I had supposed not to have written any more; but I write a few more things, that perhaps they may be of worth unto my brethren, the Lamanites, in some future day, according to the will of the Lord.

(Moroni 1:4)

Mormon had explained that he "made this record out of the plates of Nephi" when he was at Cumorah.

(Mormon 6:6)

Moroni reiterated this when he told Joseph Smith that "this history was written and deposited not far from that place," referring to Joseph's home near Palmyra, New York.

https://www.josephsmithpapers.org/paper-summary/history-1834-1836/69

Because Moroni was writing for his brethren, the Lamanites, it makes sense that he deposited the record in the area where they lived; i.e., western New York.

Cumorah "not far from" Joseph's home

That first night Moroni identified the location of the record by name: 

"the record is on a side hill on the Hill of Cumorah 3 miles from this place remove the Grass and moss and you will find a large flat stone pry that up and you will find the record under it laying on 4 pillars."

https://www.josephsmithpapers.org/paper-summary/lucy-mack-smith-history-1844-1845/41

Joseph Smith explained he knew about Cumorah before he even got the plates. 

"And again, what do we hear? Glad tidings from Cumorah! Moroni, an angel from heaven, declaring the fulfilment of the prophets—the book to be revealed." 

(Doctrine and Covenants 128:20)

This is all common sense, well documented in Church history.

Next, we consider what Moroni meant by "my brethren, the Lamanites."

Mission to the Lamanites

We know from D&C 28, 30, and 32 that the Lord described the Indians in New York, Ohio and Missouri as Lamanites when he commanded Oliver Cowdery, Parley P. Pratt, Ziba Peterson, and Peter Whitmer to go on a mission "to the Lamanites." They taught members of the Seneca, Wyandot, and Delaware nations.

- Moroni wrote his part of the record so it would be of worth to his brethren, the Lamanites. 

- That history was "written and deposited" not far from Joseph's home. 

- Cumorah is about three miles from Joseph's home. 

- The Lamanites, whom Moroni identified as his brethren, were the Indians living in western New York and those tribes who had been pushed westward from their ancestral homes.

Joseph Smith teaching the Lamanites

While in Nauvoo, Illinois, Joseph Smith told the Sac and Fox Indians who lived in the area that the Book of Mormon was the record of their ancestors.

He also wrote the "Wentworth letter" which described the Book of Mormon. Joseph adapted an 1840 pamphlet by Orson Pratt and replaced Orson's speculation about Central America by writing that the remnant of Lehi's people "are the Indians that now inhabit this country." 

https://www.josephsmithpapers.org/paper-summary/times-and-seasons-1-march-1842/5

For a comparison between Orson's pamphlet and the Wentworth letter, see 

https://www.mobom.org/wentworth-orson-pratt

So far, so good.

_____

But some LDS scholars reject all of that. They claim the early accounts about Cumorah in New York were all false speculation by the people involved. They claim that the "real Cumorah" is somewhere in southern Mexico, hence the Mesoamerican/two-Cumorahs theory ("M2C").

The M2Cers claim that instead of the history being "written and deposited not far from" Joseph's home, it was actually "written" thousands of miles away. 

Then, according to them, Moroni went on a long solitary march of thousands of miles to deposit the records in western New York, an area where his "brethren, the Lamanites" had never visited during the thousand-year history recorded in the Book of Mormon.

The M2C version of Moroni's route
(click to enlarge)

The M2Cers point to some non-scriptural and non-historical usage of the term "Lamanites" that conveyed a broad, generalized sense of the term to apply to native people throughout the western hemisphere and the Pacific basin. E.g., https://ldsmag.com/who-are-the-descendants-of-the-lamanites/

People can believe whatever they want, of course.

But everyone wants to make informed decisions. And most Latter-day Saints have never heard or seen the references from the Joseph Smith papers set out above.

And we can ask, which makes more sense?

What Joseph, Oliver, Lucy and others reported, versus what modern M2C scholars claim?