I think the expansion of terms over time is a bit damning, but originally the term was very pro-public-domain (sometimes as low as 7 years): https://en.wikipedia.org/wiki/History_of_copyright#/media/Fi...

I think we have to consider the origin of it as a concept, which predates the United States entirely and is quite a lot more damning. From the same Wikipedia page you linked:

"The first copyright privilege in England bears date 1518 and was issued to Richard Pynson, King's Printer, the successor to William Caxton. The privilege gives a monopoly for the term of two years. The date is 15 years later than that of the first privilege issued in France. Early copyright privileges were called "monopolies," particularly during the reign of Queen Elizabeth, who frequently gave grants of monopolies in articles of common use, such as salt, leather, coal, soap, cards, beer, and wine. The practice was continued until the Statute of Monopolies was enacted in 1623, ending most monopolies, with certain exceptions, such as patents; after 1623, grants of letters patent to publishers became common...

As the "menace" of printing spread, governments established centralized control mechanisms,[19] and in 1557 the English Crown thought to stem the flow of seditious and heretical books by chartering the Stationers' Company. The right to print was limited to the members of that guild, and thirty years later the Star Chamber was chartered to curtail the "greate enormities and abuses" of "dyvers contentyous and disorderlye persons professinge the arte or mystere of pryntinge or selling of books." The right to print was restricted to two universities and to the 21 existing printers in the city of London, which had 53 printing presses. The French crown also repressed printing, and printer Etienne Dolet was burned at the stake in 1546. As the English took control of type founding in 1637, printers fled to the Netherlands. Confrontation with authority made printers radical and rebellious, and 800 authors, printers and book dealers were incarcerated in the Bastille before it was stormed in 1789.[19]"

So, to summarize: the principle of copyright came from monarchic economic protectionism and censorship. I will freely admit I didn't know this piece of history before this thread - I simply predicted it, correctly, from first principles.