Great question! There is a lot to unpack here, so let's get to it.

When and why (do you think) did the New England puritans grow to be (at least in primary and secondary education) as the origins of what would become the US?

In the late 18th to early 19th this effort began, becoming solidified post Civil War. It came as a result of a battle of two myths that actually fed into that troublesome time in the mid 19th century by giving another avenue of the "us and them" mentality as both Virginia myth supporters and Plymouth myth supporters felt theirs was the true origin of America. Historians today understand neither is properly correct.

Do you perceive this as historians (or others) not wanting to source the future US in colonies established for profit with forced labor vs. a colony established for religious freedom because the latter fit better with revolutionary rhetoric (or just made for a better patriotic story)?

Not exactly. You're getting to the root with the "better patriotic story," though it was society at large and not necessarily historians themselves that concluded it's a "better" myth. And it is just that - a myth. As far as the slavery part, that existed in both places for a very long time. Legal savery was present in Massachusetts in practice before it happened in Virginia, but I'll delve into that more in depth momentarily. My point here is that it was truly a "We started America, not you!" argument between the two ideologies. They both selected parts of their origin story that fit the argument being made and that story morphed over time, the myths transitioning with that evolving need to fit the desires of the presenter(s), and both camps ignored some less than pleasant parts of their respective histories in doing so.

Let me now quote a snippet of myself from another post to set a little backdrop about the competing origination myths;

Starting in the early days of our Constitutional Republic we began to create a myth - two actually - of where America came from. Myth one was the Virginia Myth, being that Pocahontas, the Princess of Virginia, had rightly given inheritance of Virginia to the many elite families with lineage to John Rolfe, who had married the daughter of Powhatan, leader of the 30 tribe alliance known as Tsenacommacah, a territory spread mostly across the tidewater region of modern Virginia. This Myth was reinforced over time through multiple historic works, some of which either hang in the US Capital or are literally part of the wall in the Rotunda of said Capital, such as the [Baptism of Pocahontas] (https://www.aoc.gov/explore-capitol-campus/art/baptism-pocahontas) and [Pocahontas saving Capt Smith] (https://www.loc.gov/resource/ppmsca.09308/). Plays of Pocahontas were written and became wildly popular in the early 19th century, further spreading the mentality of Virginian inheritance of America, the true founding of our nation.

Myth two came from New England and was equally supported by events like Founders Day, where Daniel Webster essentially started his political career in the first quarter of the century by giving a speech and where he basically ended it about 30 years later by the same action. After all, the first historical society of any note within America was at Plymouth. In Jamestown, by contrast, wheat was grown around the old settlement by a farmer that lived there part of the year. When visitors first began to really go, again in the 1800s, it was a pilgrimage to a field of ruins and a church tower, along with some graveyards. Meanwhile in Plymouth they were trying to uncover the other half of Plymouth Rock and reattach the broken piece, while raising money for a roof enclosure for the artifact. Importantly, no Pilgram writings mention anything about a rock at all. In 1741 the residents decided to build a wharf over a unnoteworthy rock. 94 year old Thomas Faunce heard and asked that he be carried a couple miles to see it, at which point he identified it as the landing spot 120+ years earlier, saying he was told as a boy by original colonists the same. The first visitors visiting Plymouth Plantation to see history did not come for the rock, but rather to see the decapitated skull of King Philip which sat upon a pole for over 20 years (and Cotton Mather supposedly broke the jaw bone off, "silencing him forever," as one scholar put it). It also found a larger following of art than the Virginia Myth, with an equal share in the Rotunda and in popular artworks, quite a few done by John Gadsby Chapman but other artists like Charles Cope, Charles Lucy, Emanuel Leutze, and Thompkins H Matteson also painting Pilgram images all in the mid 1800s. They became so popular they even changed the way we collectively saw Pilgrams, giving them the neat costumes we know imagine with the word "Pilgram." Perhaps the most popular of them all is Robert Walter Weir's [Embarkation of the Pilgrams] (https://www.aoc.gov/explore-capitol-campus/art/embarkation-pilgrims), which hangs in the US Captial. Weir wanted to paint the signing of the Mayflower Compact, but his aquantance had planned to do that before failing to secure his bid for one of the paintings. Weir asked and the other painter became enraged, making Weir promise to never paint that subject. That enraged man would later gain his own fame for his work with the telegraph; it was one Samuel Morse.

So we see a huge buildup over the late 1700s to 1850 to create these dueling myths, one about inheriting the land properly by converting Pocahontas to Christianity (when she became Rebecca), then uniting her into Anglo rights by marriage, granting all decendents property rights over Virginia. Further north we see countless speeches from the pulpit starting very early on, followed by pop culture and public events celebrating the pious Pilgrams escaping the dark and turbulent shores of England and arriving on the sunny shores of America. And I mean they literally painted dark stormy exits and bright horizons in the distance (like Leutze's [English Puritans Escaping to America] (https://images.nypl.org/index.php?id=808094&t=w)), then calm arrivals in New England. The imagery was clear to everyone.

For more on the origination myths I suggest The Pilgrims And Pocahontas: Rival Myths Of American Origin, Ann Uhry Abrams, Westview Press (1999), which is an excellent look at the two myths in depth by Professor Abrams, an art historian, who uses art and culture to examine the debate as it happened throughout the entire 19th century.

So we have these myths - the first (by chronology of event) being a fact of patriarchal Anglican laws; man marries woman, man inherits all of woman's rights of inheritance. Example: Thomas Jefferson inherited Sally Hemings after his father-in-law, John Wayles, died while "owning" her because John's daughter, Martha, was married to Jefferson and was the senior daughter without any male siblings. Another: When George Washington was eleven, he inherited 10 humans. When he married the wealthy Martha Custis, he gained many more. That's just how the law worked back then, so Pocahontas converting to Christianity and renaming herself Rebecca made her socially acceptable, then marrying Rolfe transfered her inheritance of the kingdom to him. She was daughter of Powhatan and now it's all legally established that the kingdom existing here rightfully transferred itself to Rolfe's line. So goes the myth, anyway.

Cont'd